The Treasury has analysed the effect of Brexit on the West Midlands but won’t release the results, Chancellor Philip Hammond has said.
He said experts had produced models showing how different regions would be affected when the UK leaves the European Union.
But the findings will not be published because they are commercially sensitive, he said.
Mr Hammond was quizzed by Newcastle North MP Catherine McKinnell, a member of the House of Commons Treasury Committee.
He told her the Treasury was “constantly using” a model it had developed to look at how regions would be affected by Brexit, as well as how different sectors of the economy would benefit or suffer.
She told him: “You must understand there is a public interest in seeing these assessments and understanding the implications of them.”
Business leaders have expressed concern in the past about the effect of leaving the EU without a trade deal, and the potential difficulty some firms could face recruiting staff when freedom of movement comes to an end.
Carmakers have said it’s essential to ensure items such as car parts can be transported quickly between the UK and EU.
Theresa May has said Britain "will leave" the EU in March 2019, amid concerns from a Tory backbencher that Brexit talks could be extended.
The Prime Minister also suggested the UK's role in the EU's common fisheries policy would have to be negotiated during any transition period.
At Prime Minister's Questions, Eurosceptic Tory Peter Bone called on the Prime Minister to give an assurance "that under no circumstances will the negotiations be extended".
Mrs May responded that Article 50 did allow for an extension of exit negotiations, adding: "I've been very clear.
"We want those negotiations to end - not just the negotiations to end, we want to have an agreement on the future relationship, and our withdrawal - by March 2019, and we will leave the EU on March 2019."
Environment Secretary Michael Gove is said to be pushing for the UK to leave the fisheries policy immediately after Brexit, and not remain in it through any transition.
Liberal Democrat Alistair Carmichael, a former Scottish secretary, raised the issue during the questions session.
"When we have left the European Union, we will be leaving the common fisheries policy," Mrs May said.
"As part of the agreement that we need to enter into for the implementation period, obviously this and other issues will be part of that agreement.
"But when we leave the European Union, we will leave the common fisheries policy."