UK public sector pension funds are not big enough to generate good returns for British savers, Chancellor Rachel Reeves has told the BBC.

Her comments come as the government reveals plans to merge the UK’s local government pension scheme, a group of funds which together manage £354bn in investments, into a handful of “pension megafunds”.

The plans form part of what the government has said are the “biggest pension reforms in decades”.

It claims this will boost investment in the UK, but critics say the measures “could put savers’ money at risk”.

Reeves told the BBC ahead of her Mansion House speech that she wants the UK’s pension schemes to be more like Canada and Australia.

In those countries, the pensions of local government workers, such as teachers and civil servants, are pooled into a handful of funds which are able to make big investments around the world.

“They probably have the best pension funds anywhere in the world,” Reeves said.

The government plans to merge the 86 council pension funds – which represent 6.5 million pensions and are run by local government officials – into “megafunds” run by fund managers.

These bigger funds would also be required to “specify a target for the pool’s investment in their local economy”.

The government also wants to set a minimum size limit on defined contribution schemes, which manage around £800bn of investments, to encourage the consolidation of the around 60 different multi-employer schemes.

The government says its changes could “unlock” £80bn worth of investment into the UK in things like energy infrastructure, tech start-ups, and public services.

“Our pension funds in Britain are too small to be making the investments that get a good return for people saving for retirement and to help our economy to grow,” Reeves said.

She added it made “no sense at all” that Canadian teachers and Australian professors were more likely to be invested in many long term UK assets than savers in Britain.

However, critics say the plans could put savers’ money at risk.

“Conflating a government goal of driving investment in the UK and people’s retirement outcomes brings a danger because the risks are all taken with members’ money,” said Tom Selby, director of public policy at investment platform AJ Bell.

He said the current system encourages trustees to deliver “the highest possible income in retirement for members” rather than focus on UK-wide economic growth.

This sometimes means investing in things like US stocks and shunning the UK investment which the government is keen on.

And though bigger funds can mean bigger rewards, they can also mean bigger risks, with Canadian pension fund the Ontario Municipal Employees Retirement System being the largest investor in troubled Thames Water.

Others say there is a risk that larger funds struggle to find enough big UK projects to invest in.

“Large funds need substantial, reliable projects to generate returns, but the market may struggle to offer enough of these opportunities, especially in the infrastructure sector,” said Jon Greer, head of retirement policy at wealth manager Quilter.

He added that if “too much money chases too few viable investments” funds might be forced into “riskier” investments.

Shadow chancellor Mel Stride said the Conservatives “will be looking closely at the detail of what Rachel Reeves sets out – particularly regarding the mandating of where investments are to be made”.