Why aren’t ministers more powerful than the civil service?

The convention of individual ministerial responsibility places significant pressure on ministers. The 2010-15 coalition had multiple ministers resign over their personal behaviour.
In 2012, the Chief Conservative whip Andrew Mitchell resigned after it was alleged that he had sworn at police officers outside Downing Street.
In 2018, Amber Rudd resigned as Home Sec after she misled the Home Affairs Select Committee during a hearing on the Windrush Scandal.
In contrast, civil servants are far more anonymous, and are accountable to their minister, rather than the press and public. This allows them to provide policy advice, give recommendations, and undertake work without regular public scrutiny

Ministers, unlike civil servants, are vulnerable to negative press and elections.
Despite his popularity with party members, Michael Gove was demoted from his position as Education Secretary, to a new role as Chief Whip.
It was widely speculated that Gove’s unpopularity with teaching unions and parents sceptical of his reforms, was the main cause.
In July 2016, Gove ran as a candidate in the Conservative leadership election; however, he was eliminated in the second ballot.
He was then removed from his position as Justice Secretary by the new Prime Minister, Theresa May.
Unlike ministers, civil servants do not have to worry about keeping constituents happy, or pending general elections or leadership elections, and they are not subject to continued media attention.

The strength of ministers varies according to their personal strengths and current events – balance of power between ministers and the civil service is likely to fluctuate over time reflecting current events and can also vary depending on the personality and skill of the individual minister.
The PM might give successful ministers significant independence, but there is no guarantee that the prime minister will not take over if things start to go badly.
In April 2011, the PM announced that he was pausing controversial NHS reforms, which were being developed by the Secretary of State for Health Andrew Lansley, so that the government could listen to the concerns being raised.
By 2012, Lansley was reshuffled to a new post as Leader of the House of Commons.