Channel 4's 10 O'Clock Live returned to our screens on Wednesday night for its second series. While impressions of Tony Blair by Rory Bremner and Alastair Campbell by Peter Capaldi had accompanied Labour's time in power prior to 2010, 10 O'Clock Live represents a major attempt to update satire for the coalition era.

As such the show was afforded a fair amount of slack in its first series last year. We'd all seen and loved Jon Stewart's harpooning of America's politics and media on The Daily Show, and now here Channel 4 were promising to do the same in Britain.

When the first series failed to deliver much of a punch, therefore, we gave it a pass. So too did Channel 4 in commissioning a second run. Unfortunately, the show hasn't taken advantage of the opportunity to refresh its format and jettison those elements that don't work. It is exactly the same show as it was last year, with all of the same failings.

The show's biggest fault remains its over-emphasis on jokes. It's more than okay for satire to be funny, of course, but it must be comedy with a purpose. Satire is comedy as criticism. More often than not, in 10 O'Clock Live politics and current affairs are referenced merely as a backdrop for toilet humour.

Take Charlie Brooker's solo section during the show, which he used to discuss the Queen's diamond jubilee. He showed three clips from news footage in which several people repeated the same anecdote about how the Queen learned of King George VI's death in 1952 while at a tree-top resort in Kenya ("she went up the tree a princess, and came down it a queen..."). Rather than leaving it there, letting the material satirise itself - as Jon Stewart certainly would have - Brooker used the montage to set up a tenuous joke about ejaculation.

Jimmy Carr made the same mistake in a sketch about Vladimir Putin. Carr played Putin delivering a press conference, the punchline coming when he ripped off his shirt to reveal a bulging (prosphetic) torso. But we've already seen Putin numerous times in various states of undress. The footage of him doing it for real is far more powerful than watching Carr pretending to do it.

The great shame is that the show's creative talent should know better. Brooker himself is a master satirist. In his shows Screenwipe and Newswipe - the success of which surely prompted his inclusion in the 10 O'Clock Live team - he is adept at making the audience laugh at things other people say and do, rather than needing to make them laugh himself.

Jimmy Carr is the wittiest of the four presenters, but strangely, the self-styled joke technician looks the least comfortable in this joke-led environment. Again, this is caused by the confusion over the satiric purposes of the show. If the intention is purely to get laughs - like it is on his other show 8 Out Of 10 Cats - few can match Carr. But it's impossible to believe there's a serious point behind his jokes, because one look at his face tells you there isn't.

A related problem is that the targets of the satire are ill-chosen. Apart from the Queen and Putin, the only other people the show poked fun at in a sustained way were Ayatollah Ali Khamenei and Abu Qatada. While each might arguably be ripe for mocking, it's perplexing that 10 O'Clock Live has nothing at all to say about any serving British politician.

The only person to emerge with any real credit is David Mitchell. He produced the only moments of genuine satire, when he said he would continue to refer to former knight Fred Goodwin as 'Sir' as a reminder our failure to prevent the collapse of the banking sector, and later when commenting on how the West's sanctions regime had crippled the Iranian cardboard industry.

Mitchell's interview with the Clark Carlisle and aforementioned Alastair Campbell about football was also highly entertaining, because it was three engaging personalities putting across views they firmly believed. And without even trying it probably produced more laughs than any other segment of the show.

If 10 O'Clock Live leads to Mitchell getting his own chat show it will have achieved something worthwhile. Until that happens, the powers-that-be have little to worry about if this represents the best satire we can produce.