Hilary Armstrong, who served as the former prime minister’s chief whip, says Blair stepped in to rescue Corbyn when he was under threat of deselection

Famously, Jeremy Corbyn could not have entered the Labour leadership contest without the nominations of MPs who wanted a leftwinger in the race, although they had no intention of voting for him. But even before that, it has emerged, the veteran backbench rebel had a highly surprising secret benefactor: Tony Blair.

According to the Labour peer Hilary Armstrong, who served as the former prime minister’s chief whip, Blair stepped in to rescue Corbyn from being removed as an MP when some of Corbyn’s Islington North constituents wanted to deselect him.

Armstrong tells The Westminster Hour on BBC Radio 4 that Blair ruled out the move, taking the view that the party was “a broad church” and could “tolerate that level of difference”, despite Corbyn’s fierce and persistent criticism of his administration.

“I had folk from Jeremy’s constituency come to see me and say, ‘People are a bit upset with Jeremy always being against the Labour government, what if we try to deselect him?’”

She advised them: “You’ll get no support from the leadership, don’t bother.”

Armstrong recalls: “The prime minister was very clear about that when Jeremy was a backbench MP. And he was right; we shouldn’t have worked to deselect him. But I hope that Jeremy will now reflect on that and I hope that he will be absolutely determined to make sure it doesn’t happen under his watch.”

Current Labour MPs are concerned that they will be subjected to attempts to deselect them by Corbyn supporters. The Labour leader has declined to step in and block party rule changes that could make such deselections easier.

Armstrong called on Corbyn to intervene in a similar spirit to Blair. “The real issue is, can you make sure that sectarianism doesn’t rule? And at the moment, in some areas, it is ruling.

“Jeremy has the opportunity over the summer and at party conference to make it absolutely clear that he is not going to lead a narrow sectarian faction, he’s going to lead a broad church that is tolerant. And the real test for Jeremy is, is he up to it?”