BBC2 hit Line of Duty will return for a second series after it finished with more than 3 million viewers, making it the channel's biggest new drama for seven years.

The acclaimed Jed Mercurio series about police corruption starring Lennie James and Gina McKee had an average overnight audience of 3.2 million viewers across its five-part run, BBC2's most popular drama launch since Rome in 2005.

Line of Duty starred Martin Compston and Vicky McClure on the trail of James's tortured anti-hero, DCI Tony Gates, with a supporting cast including Adrian Dunbar and Neil Morrissey.

But the grisly finale to Tuesday's night's climax – no spoilers – mean it will have to return without one of its biggest stars as the anti-corruption unit, AC12, begins a "new and controversial" investigation.

The BBC drama controller, Ben Stephenson, said Line of Duty, made by independent producer World, was a "brilliant series ... that encapsulates my vision for bold, authored and utterly original drama on the channel".

BBC2 channel used last night's final episode, watched by 3.3 million viewers, a 15% share, to launch a marketing campaign for "original British drama" including the sequel to The Hour, starring Dominic West.

The BBC2 controller, Janice Hadlow, said she was "thrilled that this complex, contemporary drama has captured the imagination of such a loyal and appreciative audience".

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