Another man has been arrested as part of an investigation believed to be into abuse sent to Ashton-under-Lyne and Failsworth MP Angela Rayner.
On Wednesday (19 January), officers from Greater Manchester Police, alongside Sussex Police, attended an address in Brighton and arrested a 68-year-old man.
He was arrested on suspicion of malicious communications and has since been released on bail.
The arrest forms part of an ongoing investigation codenamed Operation Octant into malicious communications sent to Ms Rayner, who is also the deputy leader of the Labour Party.
The latest arrest relates to abusive emails sent on 17 November and enquiries remain ongoing, GMP say.
Four arrests have been made so far as part of the investigation, resulting in one man being charged and sentenced.
Benjamin Iliffe, from Cambridgeshire, was sentenced at Huntingdon Magistrates' Court in October after telling the MP to 'watch your back and your kids'.
A spokesperson for the MP said: "We are working with the police to ensure that the perpetrators of these crimes are brought to justice and Angela would like to thank the police for their work during these investigations.
"Abuse and threats of this nature don’t just have an impact on Angela but also on her family, her children and her staff, who are on the receiving end of these communications."
Anyone with information should contact police on 0161 856 9262 via 101 or the LiveChat function at www.gmp.police.uk. Alternatively details can be passed via the anonymous charity Crimestoppers on 0800 555 111.
If you have been a victim of hate, visit gmvictims.org.uk to access victim support and information. You can report hate crime online, via www.gmp.police.uk or by calling 101.