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Constituency Boundary Reviews

Boundary review

The boundaries of parliamentary constituencies in the UK are reviewed periodically to ensure that constituencies are broadly equal in numbers of eligible voters while also respecting local ties. In May 2020, the government proposed changes to the system of reviewing Westminster constituencies through the Parliamentary Constituencies Bill. Responding to this, the Unit launched a small research project examining the proposals. Led by Alan Renwick and Robert Hazell, it focused on safeguarding the review process from any danger of undue political interference.

The Parliamentary Constituencies Bill received royal assent and became law in December 2020; it increased the gap between constituency boundary reviews from five to eight years, and removed parliament’s ability to block Boundary Commission recommendations. Our research concludes that this is a welcome step as it upholds the principle of independence. There are no such veto rights in comparable democracies such as Canada, Australia, and New Zealand.

The government suffered five defeats at the report stage consideration of the bill in the Lords in October 2020. The changes would have extended the time between constituency boundary reviews to 10 years, increase the leeway in constituency electorate sizes from 5% above or below the average to 7.5% above or below, and invoke non-renewable terms for Commissioners and changes to the procedures by which they are appointed. The latter of these changes closely mirrored proposals made to the Commons public bill committee by Robert Hazell and Alan Renwick. Their research found that stronger safeguards are needed to protect the Boundary Commissions from interference by government. While there is no evidence of such interference to date, it would be possible under existing rules, and the removal of the parliamentary veto may increase incentives for it. Stronger safeguards already exist for many other bodies, notably the Local Government Boundary Commission for England. Implementing non-renewable terms for Boundary Commissioners would mean they are less susceptible to pressure, and setting down rules for their appointment in law would make for a more transparent process. This proposal, amongst others laid down by the Lords, was rejected in the Commons.

This work builds on Robert Hazell’s review for the government of the Local Government Commission in 1998 [Unit report no 30], which recommended merger with the Parliamentary Boundary Commission. The Unit has also done work on the independence and accountability of constitutional watchdogs [Unit reports nos 100 and 144], and on improving parliamentary scrutiny of public appointments [Unit report no 175].

Project findings are presented in three forms:

The analysis has been cited in key parliamentary debates on the bill: