The committee has recommended to the Government it should replace the current system with a new one centred around an earnings link.
It should benchmark the new state pension and basic state pension at the levels relative to average full-time earnings they reach in 2020, MPs said.
The Government has responded to say it “is committed to the triple lock for the length of the Parliament”.
Officials said the triple lock has been “an invaluable element in addressing the issue of pensioners living in low income households, which peaked in the late 1980s at over 40 per cent”.
Committee Chair Frank Field MP said: “We will continue to press for cross-party consensus on the replacement of the triple lock after 2020.
“The Government is right to say pensioner benefit spending has dipped slightly as a share of GDP, as accelerated increases in the state pension age have kicked in; but official projections show that, without reform, it will rise relentlessly from that point.
“The triple lock has been valuable but it is unsustainable. The Committee has recommended an alternative which would maintain pensioners’ living standards and protect them from the effects of inflation.”
The committee’s proposal would mean that in periods when earnings lag behind price inflation, an above-earnings increase would be applied to protect pensioners against a reduction in the purchasing power of their state pension.
The report stated: “Price indexation should continue when real earnings growth resumes until the state pension reverts to its benchmark proportion of average earnings.
“Such a mechanism would enable pensioners to continue to share in the proceeds of economic growth, protect the state pension against inflation and ensure a firm foundation for private retirement saving. e new state pension and basic state pension it replaced would track average earnings growth in the long term. at is more scally sustainable and more intergenerationally fair.”
The proportion of pensioners living in low income is now down to 14 per cent, the Government said, adding that as a result of the triple lock, the value of the full basic State Pension as a proportion of average earnings is at its highest since the late 1980s.