ITV News has obtained a recording of the call a woman made to Nick Clegg's office in June 2011 following up on a letter she says she wrote three months earlier detailing allegations of sexual misconduct against the then Lib Dem MP Mike Hancock. He denies the claims against him.
In the call, she is heard saying: "I wrote to Nick Clegg back in March  and again in May and I still haven't had a courtesy letter."
Mr Clegg said today he "acted immediately" last year when he was told legal proceedings were being taken against Mr Hancock, who has been accused of sexual misconduct. He withdrew the party whip.
But the woman's solicitor told ITV News the party was made aware two years earlier, but nothing was done.
In March 2011, the alleged victim says she wrote a letter sent by recorded delivery to the Lib Dem leader's office. The party say they did not receive it.
More top news
High levels of immigration to the UK are unsustainable and threatening the cohesion of society, Home Secretary Theresa May is to warn.
A homeless woman lay dead at a McDonald's for hours as oblivious diners ate around her.
A priest rescue several coffins that had floated away in a cemetery during unprecedented floods in the US state of South Carolina.