Lib Dem leader Vince Cable says he was in favour of working with other Remain parties to present a "common front" at the European elections. The pro-EU MP said he had approached the Green Party and Change UK to suggest joint candidates. He said the parties "shouldn't be squabbling", but added: "Frankly, we didn't get a very warm reception."
The Greens say joint lists are not "desirable" and Change UK has said an alliance "wasn't ever on the agenda". Elections for 73 MEPs to the European Parliament will take place on 23 May.
The UK had been due to leave the EU on 29 March, but the deadline has now been pushed back to 31 October, meaning the country has to take part in the polls. The Liberal Democrats pledged to stop Brexit at the launch of their European election campaign last month.
The Green Party and Change UK are also standing on pro-EU platforms. There were suggestions last week that pro-Remain parties could back a joint candidate in the forthcoming Peterborough by-election, but those efforts were not successful.
The candidate they had planned to back, Femi Oluwole, told the BBC he had pulled out over concerns his candidacy would hand victory to the Brexit Party and ultimately harm the campaign for another referendum.