Former chancellor of the exchequer Ken Clarke has said that current chancellor George Osborne should push ahead with reforms.
The Tory grandee, speaking on BBC's The Andrew Marr show, said:
When you've got yourself a mandate to put things right, get on with it quickly because you won't keep popularity very long
You've got to give time for the effects to show and put up with the difficulties because obviously everyone will protest if you do anything that isn't straightforwardly popular.
Speaking specifically about tax credits, the former cabinet minister questioned the sustainability of the system, stating that low pay is subsidised from the taxpayer in the tax credit system. "This is an obvious change to the benefits system we need to make, so my advice to George is: 'Put your tin hat on. get on with it'," Clarke added.
Don't put it off because in the short term it is going to be unpopular. Stop looking to opinion polls and listening to the more nervous backbenchers. It's bold but its necessary.
Osborne had previously come under fire from MPs, including from his own party, who were frustrated over the changes, which mean 3m families will lose on average £1,000 a year, according to research from the Institute for Fiscal Studies (IFS).
Speaking about the European Union, Clarke also said Britain defends its "interests and values when we're seen a leading influential power in the EU. That's the 21st century."
Tomorrow the "In" campaign will get started, just days after the cross-party "Out" campaign launched.