Ed Miliband and Nicola Sturgeon are "at the altar, and preparing to sign the register" on a post-election deal, according to Scottish Conservative leader Ruth Davidson.
Sturgeon made the Labour leader an offer to join forces to help him become Prime Minister during the TV debates.
But David Cameron has warned there would be more borrowing and higher taxes if Miliband goes ahead with the deal.
Ed Miliband has accused David Cameron of trying to "duck, weave and dive" his way back into power, claiming he was "gutless" for refusing to take part in a head-to-head showdown.
"I'm offering him a debate about leadership. I'm offering him a one-to-one debate about the future of the country," the Labour leader said.
"I have been saying week after week, anytime, anywhere, any place."
Miliband joked that he knew the real reason behind Cameron's absence at lat night's debate, saing, "I hear he was washing his hair".
The Ukip leader said he did not "lose my rag" when he attacked the audience during last night's televised debate for their "left-wing bias."
We watched undecided voters as they watched the debate hoping it might help them make up their minds.
Ed Miliband appeared to turn down Nicola Sturgeon's latest offer as the leaders of five "challenger" parties took part in a heated debate.