Downing Street has rejected David Lammy’s assessment that Israel has broken international law by blocking aid to Gaza, in a rare public censure for the foreign secretary.

A spokesperson for the prime minister said on Tuesday morning Israel was “at risk” of breaching humanitarian law, despite Lammy having told the Commons on Monday that the country had definitely done so.

The remarks, hours after Israel launched a wave of airstrikes on Gaza, mark a climbdown after Lammy appeared to have changed the government’s position on one of the most sensitive foreign policy questions it faces.

The public rebuke came less than 24 hours after Lammy told the Commons he believed Israel’s actions broke international law – a key test for whether the UK can continue to sell weapons to the government of Benjamin Netanyahu.