Fantasist Carl Beech made claims there was a VIP paedophile ring operating in Westminster, which were eventually found to have no basis, and was jailed.

Lord Brittan was falsely accused of sex crimes by Beech and died in 2015 aged 75 before he was publicly cleared.

Lord Watson of Wyre Forest apologised to the former home secretary's widow.

The appointment of the ex-West Bromwich East MP to the upper chamber faced criticism over accusations he "destroyed" lives by championing claims made by Beech, known as "Nick".

A botched police inquiry into the allegations, which cost millions of pounds, saw dawn raids on the Brittans' home, among others.

In the Lords, Lord Watson, 55, apologised to Lady Brittan, the widow of Lord Brittan of Spennithorne, who served in Margaret Thatcher's Conservative government.

He told fellow peers: "The first area where I think consensus is always better than disagreement is police reform.

"I apologise unreservedly to Lady Brittan for the role that I played in the investigation of historic child sexual abuse.

"Her experiences led to several recommendations about how the police conduct themselves.

"I'm sorry and I owe it to her to work to achieve those aims in this House in the months and years ahead."

After the death of Lord Brittan, Lord Watson accused the former home secretary of "multiple child rape" and quoted Beech describing him as "as close to evil as a human being could get".

A review later found Lord Watson had put pressure on investigating officers, although he disputes the findings.

Beech, himself a convicted paedophile, was subsequently jailed for 18 years for fabricating a string of claims including rape, torture and murder.

Cabinet Office minister Baroness Neville-Rolfe welcomed Lord Watson's apology, adding that it was "rightly" made.

Several peers welcomed him to the House, including Liberal Democrat Lord Wallace of Saltaire, who said: "I'm glad to be able to welcome Lord Watson, after his three years leave of absence from Westminster, he's back."

However, he has not had a warm welcome from everyone in the chamber, most notably by Tory ex-chancellor Lord Lamont, who previously branded the appointment "an absolute disgrace" and a "stain" on the Lords.