Lib Dem Lord Oates accused Labour of being prepared to "concede everything", and the opposition's leader in the Lords, Baroness Smith, responded that his party was giving people "false hope".
The two parties had teamed up to help inflict defeats on the government concerning the rights of EU citizens and parliamentary approval for a Brexit deal.
But that co-operation went out the window when MPs rejected those amendments - with Lib Dems determined to insist on them and Labour prepared to defer to the Commons.
A Labour source in the Lords told the BBC it was "fairly obvious grandstanding" by the Lib Dems, and geared towards content for their campaign leaflets.
"It's pretty unforgiveable to build up false hope with people genuinely worried about their future in Britain, when you already know that MPs were ready to dig in behind the government," the source said.
For their part, the Lib Dems' Europe spokesperson Baroness Ludford accused Labour of "waving through the government's plans" and "lining up with the Conservatives as they drive forward with a hard Brexit".
It's not just on Brexit that the two biggest opposition parties have a track record of forming alliances - they have trooped through the lobbies together to impose government defeats on bills dealing with issues from higher education to housing.
Baroness Ludford seemed sanguine about their chances of coming together again, saying: "The Liberal Democrats will continue to work with peers from across the House to fight for the issues we agree on."
But the Labour source predicted "residual tensions", adding: "I can't imagine there'll be much demand here to organise a 'progressive consensus summer drinks' gathering.
"Our respective leaderships will of course continue to keep things business-like."

Sixty patrol boats will protect the UK's two new aircraft carriers which are due to arrive at Portsmouth Naval Base in 2017.
The first carrier, HMS Queen Elizabeth, is expected to be operational in 2020.
"We are going to see a bigger Royal Navy and the flagship... will be here in Portsmouth," Michael Fallon said.
The 60 Pacific 24 rigid-hulled inflatable boats will be built by BAE systems to "guard the carriers in the harbour and our new frigates and destroyers", Mr Fallon said.
He said they will also enhance security by providing a rapid response in rescue, anti-piracy and counter-narcotics missions in the area.
Mr Fallon said: "Through the defence review, defence spending is going to go up every April for the rest of this parliament.
He said as part of the larger investment, the government will also be able to provide the new aircraft carriers with sufficient fighter jets.
"We have said we will maintain a minimum fleet of 19 destroyers and frigates, but as the older frigates are retired we also hope to add a lighter frigate between the offshore patrol vessel and Type 26 and to build more of those as well."
Mr Fallon's visit to Portsmouth Naval Base comes as work has begun to rebuild the jetty for the arrival of HMS Queen Elizabeth in 2017.
Floating cranes are also dredging Portsmouth harbour to prepare deeper channels for the aircraft carriers to sail from the base, which are the largest ships ever built for the Royal Navy.
"This is a huge financial investment in making sure the channel is wide enough, in enlarging the jetty here so they can take the carriers and in making sure the carriers are properly guarded," Mr Fallon said.
Taller than Nelson's Column and longer than Portsmouth's Spinnaker Tower laid on its side, the new carriers will displace 65,000 tonnes of water.
To make room for the carriers three million cubic metres of clay, sand and gravel will be removed from a two-mile stretch of Portsmouth Harbour covering an area the size of 200 football pitches.

Archibald, 22, dominated the event, with Dutch rider Kirsten Wild second and Belgium's Lotte Kopecky third.
That came 24 hours after she won her third consecutive women's individual pursuit title, having gained silver in Thursday's elimination race.
The Scottish cyclist won gold in the pursuit quartet at the Olympics in Rio.

The 26-year-old Samoan, who started his career with Manly Sea Eagles, made six appearances for the NRL champions last season.
He told the club website: "I'm ready now to take my game up to a new level and Castleford sounds perfect for me.
"I'm looking forward to playing for a club that plays such a big part in the community."
There were angry scenes on Monday night as the bill enabling the government to trigger Article 50 cleared the Lords.
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Increased spending will result in a "bigger" Royal Navy, the defence secretary has said, as he announced a new £13.5m shipbuilding contract.
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British Olympic champion Katie Archibald won omnium gold at the European Track Championships, her second title in two nights in Paris.
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Castleford Tigers have signed Cronulla Sharks forward Jesse Sene-Lefao on a two-year deal.