MP Lembit Opik should not face action over the publicity about his break-up with weather presenter Sian Lloyd, party officials say.
Mr Opik said he had separated from his fiancee some time ago
Liberal Democrat sources said the MP, who is in a new relationship with Gabriela Irimia, of the Cheeky Girls pop duo had done nothing wrong.
Newspapers revealed the Montgomeryshire MP had split with Ms Lloyd.
But the party's Wales and Northern Ireland spokesman told officials there was no overlap in the relationships.
He said in a statement that he and fiancee Ms Lloyd had separated "some time ago".
Mr Opik said: "The end of any personal relationship is always difficult, but these things happen."
He later said it was "not a secret" that he was going out with the singer.
Mr Opik, 41, and weather presenter Ms Lloyd announced their engagement in 2004 and had been together for four years.
The relationship break-up has attracted national media coverage, which local party officials said was "regrettable".
But BBC Wales has been told the local party does not feel the issue will affect his work as an MP.
Richard Noyce, a Liberal Democrat councillor in Newtown where Mr Opik has his constituency home, said: "The break-up of any relationship is a personal matter and I think it's regrettable in the extreme that people of the press have made so much of it.
"My view is that this remains a private matter and is deeply personal.
"I've seen Lembit Opik's statement and I hope for his sake - and indeed for Sian's sake - that the media will respect his wish."
The MP said in his statement he continued to regard Sian as one of the "brightest, most out-going, hard working and generous people I've had the privilege to know".
Gabriela Irimia is one half of pop duo Cheeky Girls
"I hope that she will remember the happy times as we both go our separate ways. I wish the very best for her," he added.
Mr Opik, who was born in Northern Ireland, has represented Montgomeryshire since 1997.
He is the Welsh Liberal Democrat leader and is an expert in near-Earth objects such as asteroids or comets, campaigning for the government to take the threat of a collision more seriously.
During their relationship, ITV presenter Ms Lloyd started teaching Mr Opik Welsh.
He proposed marriage while piloting a light aircraft, 3,000 feet above Wales.
In April this year they appeared on Celebrity Who Wants To Be A Millionaire?, winning £64,000 for charity.