David Cameron will insist he is "sticking to the plan" on the economy as his Business Secretary appeared to suggest it was time to change course.

Despite a turbulent few weeks that has seen the Government left embarrassed after its economic policy failed to deliver on the promise to protect Britain's credit rating and a by-election drubbing that heaped humiliation on Conservatives, the Prime Minister will defiantly pledge to "hold firm".

But Lib Dem Vince Cable appeared to join critics calling for a Plan B to help kick-start growth.

In a move that is likely to fuel speculation of a rift within the coalition on the Government's key economic policy he suggested capital spending, funded by borrowing, may be needed.

Mr Cameron will argue, however, that those who "falter" would plunge the United Kingdom "back into the abyss" just at a time when there were signs the Government's plan was starting to work.

In a major speech on the economy, the Prime Minister will insist his determination to stick to the austerity path the Government set in 2010 is about "doing the right thing" rather than stubbornness.

Speaking in West Yorkshire, Mr Cameron is expected to say: "I know some people think it is being stubborn to stick to a plan.

"That somehow this is just about making the numbers add up with no care whatsoever for what it means for people affected by the changes we make.

"But nothing could be further from the truth. My motives for sticking to the plan are exactly about doing the right thing to help families and business up and down the country."

Mr Cameron's visit to West Yorkshire will coincide with an announcement by BT that it is creating more than 1,000 engineering jobs in its Openreach business.