Sanctions don’t result in regime change. Whether against Iran or Russia, western countries need shrewder tactics | Simon Jenkins

Dissent cannot take hold in soil rendered barren by emigration and embargo. Political opposition needs academic and cultural exchange if it is to prosper

The chancellor of the exchequer and the IMF agree. Britain’s economy is about to take its greatest hit for decades. This is collateral damage from the US’s war on Iran and the closing of the strait of Hormuz – and will be made worse by sanctioning Gulf oil exports. Britain has already been weakened by four years of sanctions against Russia over Ukraine. Now its economic growth is to be crushed, its government’s popularity is plummeting and its prime minister may face removal.

This was what sanctions were supposed to do to the enemy, not to the UK. Their unprecedented severity was to teach Vladimir Putin the error of his ways. His friends were to plead with him to stop. Yet, in the years after sanctions took hold, Russia’s rate of economic growth was higher than Britain’s. Meanwhile, sanctions against Iran in the 2010s were meant to halt its nuclear programme. They appeared to encourage it. Now they are meant to undermine the Tehran regime and topple the ayatollahs. There seems to be little chance of that.

Simon Jenkins is a Guardian columnist