Wrightbus, the Northern Ireland-based maker of the revived Routemaster London bus, faces liquidation on Friday if a sale cannot be agreed.

The business went into administration last month with the potential loss of 1,200 jobs and has been in talks over a deal with the industrialist Jo Bamford, the son of Lord Bamford, the chairman of machinery manufacturer JCB.

The administrators, Deloitte, and the Unite union said the discussions were continuing.

However, Jeff Wright, the son of the company’s founder who owns the Wrightbus factory at Galgorm just outside Ballymena, said it was “deeply regrettable” that a sale had not been agreed and blamed Bamford.

The sale has been complicated by the fact the Wrightbus factory is owned separately from the business and is not under control of the administrators.

Bamford said he had been keen to agree terms. “At 10am this morning I made an offer to the Wright family to match the asking price for the Wrightbus factory and land,” he said. “This includes a sum to match the amount that the factory and associated land was purchased for two years ago from JTI [Japan Tobacco International].

“Mr Wright has since refused this offer and now asked for a significantly higher sum of money. We want to save this business and put it on a sustainable footing, but regrettably if this offer is not agreed today, we understand that the business will go into liquidation tomorrow.”

The Unite official George Brash, speaking outside the factory where more than 200 workers were waiting to hear of their fate, said: “It is not dead in the water, it’s hanging by a thread.”

Wright said he had been willing to sell the factory and its land, but claimed the main sticking point in the discussions was farmland that he did not consider to be part of the factory site.

He said: “It is disingenuous of Mr Bamford or his associates to suggest that there were any barriers created by my family through our land holdings.”

He added: “The facts of the matter are as follows: Mr Bamford was advised on Friday 4 October that any deal would include the entire premises at Galgorm including the factory, fixtures and fittings. These were available for lease or purchase. Mr Bamford sought to gain unrelated additional farmlands which were not for sale. It is important to note that no other bidder sought at any time to link the farmlands to the business purchase.”

Ian Paisley, the Democratic Unionist party MP for North Antrim, had earlier urged all involved to do their utmost to agree a deal, and said Thursday was “decision day”. He told the BBC’s Good Morning Ulster that Bamford had put forward a “good offer”.