Staff at a call centre where customers were described as “gazelles” to be hunted have been subjecting elderly people to dozens of calls a week to sell them expensive funeral packages, whistleblowers have told the Guardian.

Former employees at Prosperous Life, which sells more than 1,000 pre-paid funeral plans every month, said they had felt under pressure to push people to sign up for schemes with little regard for their income. They said that high-pressure sales tactics existed alongside a company culture inspired by The Wolf of Wall Street movie.

The Funeral Planning Authority’s code of conduct – which Prosperous Life does not subscribe to – states that firms “must not pressurise potential customers to buy funeral plans”. But multiple ex-employees say that they felt under pressure to push people into signing up.

Prosperous Life dismissed the claims and told the Guardian that it abided strictly by minimum income levels. It said that any customers who changed their minds about purchases were refunded in full.

The company, co-run by a former Premiership rugby club owner, claims to be one of the country’s leading funeral providers and says it prides itself on its “reputation and expertise”. However, the whistleblowers, who worked at the firm earlier this year, claim:

• Staff were instructed to suggest that low-income customers who said they could not afford deposits for the £4,000 packages should split their payments over several weeks – even if they had to use a credit card to do so.

• There was an aggressive sales culture with management and staff referring to themselves as “lions” and potential customers as “gazelles”. A life-sized cardboard cutout of Leonardo DiCaprio as the disgraced fraudster Jordan Belfort in The Wolf of Wall Street movie was placed in the office.

• Households continued to be subjected to dozens of calls – even after they said they were not interested or hung up on sales people. One customer said he received 57 calls in a week.

• In some cases staff breached the Data Protection Act by tricking customers into giving personal details to complete customer records – by pretending they already had them and simply needed confirmation.

The firm denies that it acts irresponsibly, calls customers excessively or breaches the Data Protection Act. It said that the Jordan Belfort cutout was used as part of compliance training and that the “lions and gazelles” descriptions were taken from a motivational training video.

One whistleblower said they had been left upset by their experience of sales practices at the firm, and would be furious if their grandmother was treated in the same way. Of their decision to leave the company, they said: “Despite the high pay, I could no longer justify it to myself.”

Prosperous Life, which employs more than 100 people, has a call centre in Cheadle Hulme, near Stockport, in Greater Manchester. It is co-owned and co-directed by the double glazing tycoon Ian Blackhurst and his wife, Belinda. Blackhurst, who lives in an historic £5m house set in National Trust parkland, co-owned the Premiership rugby club Sale Sharks for 16 years, until 2016. The other director, James Murtagh, previously the director of a debt management firm, owns the other half of the company.

The firm sells funeral plans, costing between £3,595 and £4,195, which allow customers to pay for the cost before they die in monthly instalments over several years. The packages include funeral director’s services, a hearse, a coffin and up to £1,000 for third-party fees such as cremation or cemetery fees.

The funds are held in a trust, with Prosperous Life selling plans held in one operated by another leading firm, Pride Planning. It has also started selling funeral plans using its own newly established Great British Funeral Trust to hold the funds. Pride Planning said it was “extremely concerned” to hear the whistleblowers’ allegations and had launched an investigation.

Former employees said that they had felt under pressure to push people into sales regardless of their circumstances.

One whistleblower, who left the company earlier this year, told the Guardian: “Managers would often listen in to your calls with potential customers when you were at the stage of closing the deal and explicitly instruct you to push them into signing up. But even when they weren’t listening, there was an unspoken pressure to go to whatever lengths to get the sale.

“I saw staff crack because of it and cry at their desks. There was a culture of pressure from the top which meant that elderly people, some of whom would be surviving on benefits, were sold funeral plans I don’t believe they could afford.”

The whistleblower said: “One of the things I felt particularly uncomfortable with was at first when you go on to the sales floor, the only thing I’d get given were ‘under income’ leads. So they’d be less than £800 a month in terms of their income. Naturally, a lot of these under income people were vulnerable, you can just tell.

“I’d put a lot of pressure on these people to get a deposit. The minimum deposit was £150 or £100 – it later changed. You’d encourage them to do it on their credit card. I knew they could never afford £45 a month for a funeral plan but you sort of guilt trip them into it.

“Many of the clients which we did deferred deposits on were surviving on little more than a state pension, which is why they could not afford the £100. The money would then be taken on their payday leaving them with little to live on for that month in some instances.”

Staff said they were encouraged to go ahead with sales even if they were concerned they might later be cancelled because the customer had granted power of attorney over their finances to someone else – which could indicate that they were vulnerable.

Another whistleblower said: “It was very much, just say what you need to say and we’ll deal with the shit later.” Prosperous Life said it was unaware of any such instances.

Whistleblowers said they would also call up people previously assessed as “under income, can’t afford” in the hope that their situation had changed.

“It would be a case of, ‘I’m here to help you, so you need to tell me what your monthly outgoings are’. It was just very, ‘you are doing this, and you are doing this with me today’.”

In June, the government announced plans to regulate the £2bn funeral plan industry through the Financial Conduct Authority. But the government has yet to alter the necessary legislation to bring it into force.

A spokesperson for Prosperous Life, also known as Late Life Planning (LL), denied the firm targeted lower-income customers, saying that it responded to specific requests from people to be contacted about funeral plans. The company also said it did not “knowingly sell to vulnerable customers”.

The spokesperson added: “There is a three stage process and all customers are contacted by an in-house compliance officer to ensure they are happy to proceed with the plan. If at any stage LL is notified or is concerned that a customer is vulnerable and/or unable to give proper instructions, LL will respond accordingly. LL is unaware of any such instances as claimed.”

It denied breaching the Data Protection Act and said it had received no formal complaints from customers.

The Information Commissioner’s Office confirmed it had received “a number” of complaints about Prosperous Life and was “making enquiries”.

A Pride Planning spokesman said the firm “does not condone any high pressure sales activity, and we work to extremely high standards – we expect the same high standards to be upheld by our panel of referrers”.