Liberal Democrat MPs have criticised their party leader over his defence of the pension triple lock.

Senior Lib Dems, who are on the party's frontbench, have privately attacked Sir Ed Davey for his response to the prime minister's plans to adjust the policy, which guarantees the state pension goes up each year in line with either inflation, wage increases, or 2.5% – whichever is highest.

They joined unsolicited criticism in public and private from others in the party, with one saying the majority of Lib Dem MPs disagree with their leader.

It comes after Sir Ed told the BBC removing the triple lock "would put more pensioners into poverty".

"This would mean people who are working hard now - the millennials - when they retire would have a very poor pension," he told the Today programme.

Under Andy Burnham's plan - which he hopes will raise £15bn a year by the end of the 2030s - the automatic annual link with average earnings would be removed from 2030 so the state pension rises with at least 2.5% or inflation, whichever is higher.

"His proposals are to deal with social care in the next decade when it needs to be done now," Sir Ed said.

"It's a little bit of a vibe. It's not a solution," he said.

But multiple Lib Dems at different levels have now criticised Sir Ed's response.

Could changing the pension triple lock pay for Burnham's big social care plan?

What is the triple lock and why are people talking about it?

A Lib Dem MP contacted the BBC after Sir Ed's interview to say the majority of the parliamentary party would not support opposing Burnham's changes to the triple lock.

Another, Tom Gordon, who represents Harrogate & Knaresborough, said Sir Ed's criticism of Burnham's plan to adjust the triple lock was "nonsense" and "gaslights an entire generation into believing it's for our benefit".

He wrote on X: "The idea that we're keeping the triple lock to help millennials is at best for the birds, and at worst downright insulting. I say that as a millennial."

He added: "Telling millennials we're keeping the triple lock to help us in 30 years' time is nonsense.

"We're on course to be the first generation worse off than our parents. We're locked out of the housing market, paying higher taxes, repaying student loans that never seem to shrink, and putting off having children because of the cost of living."

Vikki Slade, the party's MP for Mid-Dorset and North Poole, said on Bluesky: "Most millennials don't think there will be a state pension when they retire so this isn't being done with them in mind."

She added that she was "proud" of the triple lock when it was introduced by the Conservative-Liberal Democrat coalition government in 2010, "but we must plan for future not venerate the past".

A Lib Dem spokesperson said: "The triple lock has always been controversial.

"It's done a lot of good but its job isn't done yet, so Labour's plan would push too many of today's workers into poverty when they retire.

"We want Andy Burnham to get back around the table so that we can find a lasting consensus on social care with a sustainable funding model - not one pulled out of the pockets of a group of people who can least afford it."

The Lib Dems, and other opposition parties, are battling to respond to a new set of priorities from the Labour government under Burnham.

One frontbench Lib Dem MP told the BBC after Burnham's Labour conference speech: "Lots of us [are] struggling tonight with [a] Labour leader articulating Lib Dem values better than we do."

They pointed to Burnham's promises on electoral reform, social care, the water industry, and relations with Europe - all Lib Dem campaign points in recent years.

"I'm honestly utterly despondent with the state of things," another Lib Dem MP said.

Some senior Lib Dems believe Sir Ed's position as leader has been vulnerable for some time, even if they stressed no challenge is imminent.

"A plausible candidate could take him tomorrow in a bloodless coup," one prominent party figure said.

"But that person hasn't yet revealed themselves as far as I'm aware. Nobody is going to blow anything up without a clear plan to put something in its place."

Sign up for our Politics Essential newsletter to keep up with the inner workings of Westminster and beyond.