Mr Portillo was among Tory government ministers who lost their seats at the 1997 general election.

He told Talk Radio: "I think about going into parliament, probably at the next election.

"To me, going back into parliament is a tall step to climb."

In recent weeks, Mr Portillo has re-opened the euro row by urging Tory leader William Hague to take a stronger stand over the issue of single currency.

Questioned about possibly replacing Mr Hague, Mr Portillo said he had no desire to lead the Tories in opposition.

William Hague: "A good leader"

He said: "I'm not particularly interested in leading a party. I want to be in government and get things done.

"I'm not William Hague's equal as a parliamentary performer.

"I think William Hague is a good leader and I want to see him succeed."

In a letter to The Telegraph earlier this month, Mr Portillo implied he still had widespread support.

He wrote: "There is a profusion of organisations campaigning against British participation but they need to be led. The Conservative party is the only body with the political weight and experience that can do so."

At the time, former deputy prime minister Michael Heseltine warned that he thought Mr Hague should be worried by the former cabinet minister's intentions.

The former deputy prime minister said it was virtually certain Mr Portillo would challenge for the leadership in the future.

He told the BBC: "It's quite obvious, when Michael comes back there is going to be a concerted campaign, in which newspapers like the Telegraph will play a significant part, in order to replace Hague with Portillo.