Damian McBride, who was forced to resign as former prime minister Gordon Brown's adviser in 2009 after being linked to a plot to smear Tory MPs on a gossip website, said:
Labour currently has no clear idea who its target audience is, no positive messages to communicate to anyone about why they should vote for the party, no policies which will persuade them, and is being run in a totally dysfunctional way.
The former spin doctor urged Labour to acknowledge its mistakes in government and to better communicate a coherent plan for the country. He wrote:
If Labour currently has central, underlying messages that it is trying to communicate to the electorate about itself, its policies, and its leader, the best you could say at present is that it's not quite coming across.
If the message is 'We're not the Tories or the Lib Dems, and you hate them', that may work up to a point, but it won't do much for those people who would happily express their antipathy by voting for Ukip or just staying at home, let alone those who hate Labour as well.
More top news
More than 1.85 million people have called for the US president's visit to be watered down to avoid causing "embarrassment" to the Queen.
Jim Mattis arrived in Baghdad on the day after US-backed Iraqi forces launched an operation to reclaim Mosul from IS.
The scale of the blood poisoning disease sepsis is "far worse" than previously thought thanks to a "crippling" lack of data, a study says.