The personal details of millions of voters are believed to have been accessed in an attack by China on Britain’s democratic process.

With the UK under pressure to respond, multiple reports suggested that sanctions against individuals thought to be connected with the alleged activity are under strong consideration.

A small group of politicians who are hawkish on China are said to have been called to a briefing by parliament’s director of security, Alison Giles, in relation to the activity.

They include former Conservative leader Sir Iain Duncan Smith, the former minister Tim Loughton, the crossbench peer Lord Alton and the SNP MP Stewart McDonald, the Times reported.

The four are members of the Inter-Parliamentary Alliance on China (Ipac) pressure group, which focuses on issues involving the increasingly assertive Asian power.

At an Ipac meeting on Friday, Luke de Pulford, its executive director, said: “About a year ago the Belgian and French foreign ministries publicly confirmed [Chinese state] sponsored cyber-attacks against our members.