“The ‘grey vote’ holds significant importance,” he said.

The manifesto confirmed a range of key pension measures. It reaffirmed the Tories’ commitment to retain the state pension triple lock for a further five years, offering state pensioners a guarantee of increases equal to the highest of price inflation, earnings growth or 2.5%.

Mr Cameron said: “There has been much speculation over the sustainability of this, but a return to typical historic levels of inflation and earnings growth may make it less costly or unpredictable in future years.”

As previously trailed, the Conservatives said they would go further under their Triple Lock Plus plans, a commitment to increase state pensioners’ personal allowance in line with the state pension triple lock.

Mr Cameron said: “The manifesto also confirmed the Conservatives won’t change the system of pensions tax relief for the next five years, retaining a top-up based on an individual’s highest marginal rate of income tax, which is very valuable particularly to higher earners. There’s also a commitment to the 25% tax free lump sum and no new or increased pension taxes.”

But he added that unfortunately, a number of important future pensions developments didn’t get a mention. These included when enhancements to automatic enrolment might be advanced. They would open up automatic enrolment into workplace pensions from age 18 rather than 22 and would gradually increase the minimum contributions to 8% of earnings from the first £1, rather than only on earnings above £6,240.

Mr Cameron said: “Now that the Conservatives have set out their stall on pensions, we await the Labour manifesto on Thursday to see how it compares.”     

Simon Kew, head of market engagement at independent pensions consultancy Broadstone, said there were no surprises on pensions reform in the manifesto.

He said: “The previous commitment to a ‘Triple Lock Plus’ to protect the state pension from being dragged into income tax was reaffirmed. The proposed National Insurance cut for the self-employed will support their financial health and it is positive that this will not impact their state pension, but we would have liked to see further detail of a plan to boost adequate pension saving among this group.

“For the pensions sector it appears to be a continuity manifesto with myriad existing reforms still going through the legislative process.”

Tom McPhail, director of public affairs at consultancy the Lang Cat, said the cuts to NI raise questions about the sustainability of the state pension.

He said: “On the one hand they’re cutting national insurance which funds state pensions, but on the other, making promises to retain the triple lock. While the promise of a pensions tax guarantee of no new taxes on pensions adds little to the debate.

“As a matter of urgency, we need to have a sensible conversation about what a sustainable, adequate and fair pension system looks like.  This constant tinkering with the UK’s pension system highlights yet again, the need for a long-term savings commission to establish a consensus, drive reform and provide continuity regardless of changes in government.”

Tom Selby, director of public policy at AJ Bell, also called for simplification of the pension tax system. He said: "Pensions have suffered from near-constant tinkering over the last 14 years, an approach which has layered on complexity and created huge uncertainty for long-term savers.

"In particular, the complex set of annual allowances that currently exist are a barrier to communication of the benefits of saving for retirement.”