Discussions with Nissan before the carmaker’s decision to expand its UK operation were “open and honest”, Downing Street has said.
There was “no deal, no compensation package, nothing about tariffs”, a No 10 spokesman said.
The Times reported that ministers had given a “last-minute written promise” to protect Nissan from the consequences of Brexit to keep investment in the UK.
Labour has said the government should say what was promised.
Business Secretary Greg Clark is to be questioned on the subject by MPs.
Nissan announced on Thursday that it would build two new models at its Sunderland plant following talks with the government, securing 7,000 jobs.
The Japanese company’s commitment to the UK’s biggest car factory had been in doubt following the referendum decision to leave the European Union.
Downing Street has been asked to confirm the Times report that a written promise was made to protect the company from any consequences of Brexit, such as possible increased trade tariffs.
The prime minister’s spokesman said there had been “numerous discussions” between Nissan and the government.
Pressed on whether a letter had been written to the company, he said there were “all forms of communication between Nissan and the government at various levels” and that it would get the “best deal” for all industry when the UK leaves the EU, which is expected to happen in 2019.
But Conservative MP and former business minister Anna Soubry said that “something has been put into this, effectively a sweetening of a deal, to keep Nissan in our country”.
She told BBC Radio 4’s The World at One: “The public will want to know if there’s been some guarantee, some commitment that involves the spending of the public’s money. I think taxpayers, the public, are entitled to know because it’s their money.”
Ms Soubry warned that the government might have “opened up a very difficult can of worms”.
If it had decided to help car makers, it would have to do the same for all other sectors, such as aerospace and pharmaceuticals, she added.
MPs will question Mr Clark about the deal when he appears before the Business Energy and Industrial Strategy Committee within the next few weeks, chairman Iain Wright said.
The Labour MP said this should form “quite a large part” of the scheduled hearing, adding: “I want to really question him on: What are the terms of the deal? Is it cash? Is it indirect assistance? How long will that be on for and what other companies and sectors will be entitled to such reassurance and support?”
He said: “The prime minister and the business secretary say, ‘Trust us on this one.’ I’m not sure whether that would provide the reassurance Nissan would want. So what has been offered?”
But a senior Nissan Europe executive, Colin Lawther, said the company had received “no special deal”.
“It’s just a commitment from the government to work with the whole of the automotive industry to make sure the whole automotive industry in the UK remains competitive,” he told the BBC.
“We would expect nothing for us that the rest of the industry wouldn’t be able to have access to. We see this as a whole industry thing, not a Nissan thing.”
Labour leader Jeremy Corbyn said the government must disclose any deal struck with the firm, saying it could not hide it from the public.
The Sunderland plant produced 475,000 vehicles last year – 80% of which were exported.
Nissan talks were open and honest, says Downing Street}