LONDON (Reuters) - Former British energy secretary Chris Huhne pleaded guilty on Monday to perverting the course of justice by persuading his then wife in 2003 to accept penalty points on her driving license for a speeding offence he had committed.

A senior member of the Liberal Democrats, the smaller party in Britain's ruling coalition, Huhne resigned from his cabinet post in February 2012 when he was charged.

He had remained a member of parliament but said after the Monday London court hearing that he would quit his seat.

Huhne remains free on unconditional bail pending his sentencing, which judge Nigel Sweeney said would take place at an unspecified later date. The judge signaled to Huhne that he was likely to face a term in jail.

"You should have no illusions whatsoever as to the sort of sentence that you are likely to receive," Sweeney told Huhne after he entered a guilty plea.

"Understood?" the judge asked Huhne, who nodded from the glass-walled dock at the back of the courtroom.

At a court hearing a week ago, Huhne had pleaded not guilty to the same offense. His ex-wife Vicky Pryce, who was charged with the same offence at the same time, had pleaded not guilty at an earlier court hearing.

Outside the court, Huhne said he would be standing down from his parliamentary seat in Eastleigh in southern England.

"Having taken responsibility for something which happened 10 years ago the only proper course of action for me is now to resign my Eastleigh seat in parliament," Huhne told reporters.

A heavyweight among Liberal Democrats, Huhne narrowly lost to Nick Clegg in a 2007 election to lead the party. Clegg is now deputy prime minister in a coalition government led by Conservatives.

Describing Huhne as "a big beast", Clegg recently told reporters he would like to see the ex-minister return to the "top table" of British politics, were he cleared of the charges.

(Reporting by Estelle Shirbon Editing by Maria Golovnina)