The next Prime Minister will need to limit their ambitions beyond Brexit

Top of the new Prime Minister’s in-tray will undoubtedly be Brexit, and the need to either get a new deal through Parliament or prevent MPs from blocking no deal. But both leadership contenders have also unveiled a raft of domestic policy pledges during the campaign, from major changes to tax and spending to reform of adult social care. Many of these will need legislation. As Amber Rudd has warned, whoever wins the contest will be in for a parliamentary reality check.

The new PM will still have a tiny majority – and it may get smaller

The biggest parliamentary challenge facing the new PM is a tiny working majority in the House of Commons. After the last general election, and the loss of her majority, Theresa May abandoned many of the biggest pledges in her manifesto. Despite her ‘confidence and supply’ deal with the Democratic Unionist Party, May’s initial working majority of 13 has steadily eroded due to defections and resignations. It currently stands at just four MPs (as Tory MP Charlie Elphicke has been suspended from the party pending criminal investigation). The Government’s majority may decrease further if the Conservatives lose the Brecon and Radnorshire by-election in August.

Shifting loyalties could also upset the parliamentary arithmetic. Previously loyal Cabinet members who are staunchly opposed to no deal are widely expected to be sent back to the backbenches and may not help the Government's cause. There could also be further resignations from the Conservative Party. It is not impossible that the Government could lose its working majority entirely (though it would still have to lose a formal vote of no confidence to fall).

Backbenchers will wield significant power

A small majority gives backbenchers leverage over the Government. Throughout the current parliamentary session, ministers have had to accept backbench amendments or make other concessions to try and avoid defeats – a strategy that has become less successful as political divisions over Brexit have got worse. The new PM may decide that he is willing to gamble on a few defeats – or feel that Government defeats have become so frequent that they are not a threat to its survival. But the political risks remain high.

The next Prime Minister might want to follow Theresa May’s approach of reducing the opportunities for backbenchers to hijack Parliament by introducing few bills and filling time with general debates. For a new PM keen to demonstrate his fresh agenda this would be an extraordinary testament to the numerous parliamentary challenges he faces. However, if the new PM wants to hold an emergency budget, or impose direct rule in Northern Ireland to deal with the fallout from no deal, then he will be unable to avoid new legislation for long.

Recent amendments have made things harder for the new Prime Minister

The recent Northern Ireland (Executive Formation) Bill 2017–19 clearly demonstrates the risks posed by introducing new legislation. Successful amendments now require the Government to extend abortion rights and same-sex marriage to Northern Ireland if devolution isn’t restored in October – potentially putting it in an awkward position with regards to its socially conservative confidence-and-supply partners. 

Other amendments to the bill could set up further parliamentary flash points in the Autumn. The bill now also requires the Government to report to Parliament on the progress made to restore devolution in Northern Ireland, and MPs and Peers to debate these reports. This potentially paves the way for MPs to take control of the parliamentary agenda and introduce legislation to prevent no deal. The tight numbers and significant opposition to no deal among MPs could make it difficult for the new Prime Minister to fend off such moves, and the amendments also make it harder for them to by-pass their opponents by proroguing Parliament.

The new PM has two options: a limited agenda or a general election

Theresa May’s successor could try to improve the fractious relationship between Parliament and the executive. Andrea Leadsom, the former Leader of the Commons, told the Institute for Government that greater transparency could help. But it’s unclear what form this would take. In any case, there is little time to make amends, and the political situation means this relationship only looks set to worsen. Talk of prorogation will not have helped – and even if the new PM takes a more conciliatory approach to Parliament, it will not change the difficult arithmetic.

With a fragile and unstable majority, and deep parliamentary divisions over Brexit likely to dominate the coming months, the ability of the new occupant of Number 10 to pass legislation – or fend off his opponents – will be limited. He will need to make a choice. Either, like Theresa May, he accepts these constraints and limits his ambition beyond Brexit. Or, as Boris Johnson is said to be considering, risk a general election to try and improve his majority. Either way, a parliamentary reality check awaits.