Ben Wallace says helium volition resign arsenic defence caput astatine the adjacent Cabinet reshuffle.
He told the Sunday Times helium would not basal astatine the adjacent wide election, but ruled retired leaving "prematurely" and triggering a by-election.
Mr Wallace has served arsenic defence caput nether 3 antithetic PMs and played a high-profile relation successful the UK's effect to the warfare successful Ukraine.
Sources told the BBC they expect the adjacent reshuffle successful September.
His Wyre and Preston North constituency is acceptable to vanish nether upcoming bound changes and helium told the paper helium would not question a caller one.
The announcement comes aft days of speculation that helium mightiness permission authorities aft 4 years successful the role.
He has antecedently served arsenic a curate successful the Northern Ireland section and successful the Home Office.