A House of Commons spokesman said the investigation was ongoing

Lord Lester of Herne Hill has also withdrawn from the party whip while an investigation is carried out into the claims by the House of Lords Commissioner for Standards.

The peer has told The Sun he adamantly denied the historic allegations and would “vigorously contest” them.

A Lib Dem spokesman said: “Anthony Lester has withdrawn himself as a spokesperson in the Lords and membership of the Liberal Democrat group in the Lords whilst the investigation by the House of Lords Standards Commissioner is ongoing.”

Lord Lester, 81, a prominent QC, was the party’s spokesman on human rights.

The commissioner for standards lists the peer as the subject of one of its current inquiries.

It says an investigation is being carried out into an “alleged breach of the code in relation to personal honour”.

The allegations reportedly relate to inappropriate behaviour a number of years ago.

A spokesman for Lord Lester told The Sun: “Lord Lester has a long and distinguished record as a champion of human rights and sex equality and has a right to be treated fairly and under due process.

“He will vigorously contest the allegation.

“In the meantime he has withdrawn himself from his position as a spokesperson in the Lords and from his membership of the Liberal Democrat group in the Lords until this issue is resolved.”

PA