Cabinet ministers are plotting to axe Britain’s pledge to spend 0.7% of national income on foreign aid so they can promise in the next Tory election manifesto to divert more cash to the armed forces.

Under sweeping plans being mapped out for 2020, Downing Street also wants to scrap the Fixed Term Parliaments Act, which sets the time between general elections at five years and robs prime ministers of the freedom to call a vote at a time of their choosing.

Senior Conservatives say a decision has also been taken “in principle” to scrap the pensions “triple lock” guarantee because it is too expensive.

All three proposals are likely to generate significant opposition but are under consideration for the manifesto if the Tories remain in