The one-off drama, under the working title of A Very Social Secretary, will star Bernard Hill and Blunkett, Victoria Hamilton as Kimberly Quinn and Robert Lindsay as Tony Blair.
Launch night of the channel will also see the first edition of The Last Word, a sideways look at the day鈥檚 events that will be fronted by a rotating line-up of presenters including Stanley Johnson, father of Tory MP Boris, plus David Mitchell and Mark Dolan.
Channel 4 has pledged two-thirds of the More4鈥檚 拢33m programme budget will be spent on original, British content.
Morgan Spurlock, thorn in the side of global fast food outlet MacDonald鈥檚 after his Oscar-nominated movie Super Size Me, will present The Last Word for a week and viewers will also see the premiere of his new documentary series, 30 Days.
More4 is expected to roll out programming already aired on other Channel 4 strands such as The Madness of King George, The Crying Game and Dance With A Stranger, from FilmFour, plus repeats of documentaries Demolition, Jamie鈥檚 Great Escape, Priest Idol and Monarchy.
Chief executive Andy Duncan said: 鈥淲e鈥檙e understandably excited about our launch line-up and convinced that More4 represents a significant extension of choice for our viewers.
鈥淣o other commercial broadcaster in the UK would contemplate launching a free-to-air channel with the richness and creative ambition of More4, which aims to make a significant public service contribution in its own right.
More4 is the third digital and cable offshoot since the launch of Channel 4 in the 1980s.
FilmFour was unveiled in November 1998, while E4 was launched in January 2001.
Peter Dale, head of More4, said: 鈥淭hese are programmes of a scale and an ambition that would not seem out of place on Channel 4 itself and yet are very thin on the ground elsewhere in the digital TV universe.
鈥淭hey sum up what we want More4 to be 鈥 a lively, outspoken and above all entertaining channel for discerning viewers who want more from digital TV than repeats, football and back-to-back acquisitions.鈥
By Kevin May
More4 prepares for October launch
Channel 4鈥檚 new cable, digital and Freeview offshoot More4 will air for the first time on Monday 10 October with a drama about last year鈥檚 scandal involving home secretary David Blunkett.