Fitzgerald says the lifetime allowance on pensions – currently £1.25m – is putting off savers as young as 45, who have chosen to stop saving into pension funds for fear of incurring onerous tax charges by hitting the cap.

Fitzgerald said: “Some 45 year olds with 20 years to go are already deciding not to save more into their pensions because of the cap. They are missing out. Our message on 40% pension tax relief is ‘buy now while stocks last’ – it won’t be around forever and these people may miss out.”

Fitzgerald points out that tax relief for higher and additional rate taxpayers could be as high as 70 per cent when the benefits of salary sacrifice, tax relief and the return of child benefit are taken into consideration. However, Fitzgerald believes these rules may soon change.

He said: “This may be a narrowing window of opportunity. Labour is talking about basic tax relief only on pensions, as are the Liberal Democrats. The Conservatives are being very quiet. I would be willing to bet 40% relief will not be around forever.”

By contrast figures from Brewin Dolphin indicate that a 45 year old with a £350,000 pension pot and monthly contributions of £1,000 will take two decades to hit their lifetime allowance, assuming six per cent growth per year. Even those who do hit the cap can use drawdown to chip away at their savings from age 55, moving them away from their lifetime limit.

Fitzgerald said: “No one is telling people about this. They should get the tax relief while they can and think about [how to deal with the lifetime allowance] later.”

Fitzgerald urged the government to foster stability in the pensions system, arguing that continuously changing rules were destroying faith in the structure and driving savers to potentially risky investments such as buy-to-let.

“You could argue that the government is funding the housing bubble,” he said. “Unless people are reassured, they may stop using pensions altogether, which is not what the government wants.”