Police have been called in by the Liberal Democrats to investigate allegations against the party's former chief executive, Lord Rennard.

Scotland Yard said it was investigating "whether or not criminal activity had taken place" after being contacted by the party, the Coalition partners in Government.

It follows allegations of inappropriate behaviour from a series of women.

The news came as the LibDems announced they had set up a helpline for women with concerns over the behaviour of the former senior party executive.

As pressure increased on senior party figures over what they knew and when, LibDem women's minister Jo Swinson refused to be drawn on her statement that she had taken "action" after allegations were put to her.

In a significant shift, Lord Rennard also admitted for the first time that he had a conversation with Danny Alexander after rumours over his behaviour surfaced in 2008.

The peer has strongly denied all the allegations against him.

Party leader and Deputy Prime Minister Nick Clegg also appeared to shift his position again on the allegations, saying he had not been aware of "very specific" accusations.

The LibDems insisted at the weekend Mr Clegg had known nothing of the claims before they emerged last week.

But on Sunday he admitted that anonymous and non-specific rumours had reached his office by 2008.

A spokesman for Scotland Yard said it had been approached by LibDem officials and it was "working with them to ascertain whether or not criminal activity has taken place".