Grant Shapps was accused of dodging the question as he clashed with Trevor Phillips over HS2.
The defence secretary repeatedly failed to say whether the next phase of the multi-billion pound project will go ahead.
Speculation is mounting that the government will axe plans to extend the rail line from Manchester to Birmingham.
Appearing on Sky News this morning, Shapps was asked whether or not he had promised businesses HS2 would go ahead as planned while he was transport secretary.
Phillips said: “Did you personally encourage people to invest on the basis that it was to run from central London to Manchester?”
Shapps began to say: “We’ve invested...”
But Phillips told him: “You’re answering a different question.
“I’m asking you when you talked to businesses as transport secretary, did you say to them, ’look, it’s worth investing in the north in this way because there will be HS2. Did you?”
But Shapps failed to answer and instead repeated that “the government is committed to improving rail infrastructure, particularly in the north”.
He added: “Forgive me, Trevor. I think your viewers understand that I’m not here today to deliver the budget on your excellent programme.
“I’m here to talk about actually things that I can inform you about which is for example, in my role as defence secretary and our work in Ukraine.”