She becomes the ninth Labour MP to quit the Commons after several big names announced their retirement, including Alan Johnson.
Ms Mactaggart was one of just 13 MPs who voted against holding a snap general election after Theresa May called for a poll to be held by the summer. The 8 June vote won the backing of 522 MPs.
The timing of her announcement was awkward for the Labour leader, who was mid-speech at the party's first key rally when the news broke.
In a memo sent to her Labour colleagues, the MP for Slough said she was “bored by political squabbles over personalities” and “depressed by the way the fantastic capacity in the voluntary sector is being run down by lack of funds or poor leadership”.
“People in Slough still face many problems,” she said in the email to local party members.
“For some years now I have had to tell constituents living in miserable overpriced and overcrowded homes that they are unlikely to qualify for a secure tenancy that they can afford.
“I have been frustrated by cruel immigration rules which prevent families from living together in this country where they are citizens while inefficient administration means that some people easily flout the rules.
“I am embarrassed to discuss with our headteachers how they will cut spending to fit the meagre budgets they face.
“I have been depressed by the way the fantastic capacity in the voluntary sector is being run down by lack of funds or poor leadership.
“I have been bored by political squabbles over personalities and I know I don’t still have the passion which has driven my politics for 20 years.”
She also criticised Ms May for sacrificing two months of the two-year Brexit negotiation to hold another vote.
"I cannot believe that spending eight weeks of a time-limited negotiation period campaigning in an election rather than talking to our EU partners will strengthen her hand in negotiations with anyone outside her own conservative party," she said.
Ms Mactaggart, first elected in 1997 when Tony Blair swept to power with a landslide victory, is currently a member of the Intelligence and Security Committee.
The former Home Office minister has also been an active campaigner on slavery and trafficking. She is the secretary of the All-Party Parliamentary Group on Prostitution and the Global Sex Trade and co-chair of the All-Party Parliamentary Group on Human Trafficking & Modern Day Slavery.
Other Labour MPs not contesting the 8 June vote include former shadow home secretary Andy Burnham, who is running to be the metro mayor of Greater Manchester, and Brexiteer Gisela Stuart, a long-time critic of Jeremy Corbyn.Reuse content