Mr Exley previously worked as director of internet campaigns for the Democratic Party in the US.
He also famously published a satirical political site under the domain name gwbush.com, prompting President Bush to call Mr Exley a "garbage man" and say that "there ought to be limits to freedom".
A Labour spokesperson would not comment on Mr Exley's role, stating that the party "does not discuss internal staffing matters". But his appointment is likely to encourage speculation that Labour is developing new ways to campaign and co-ordinate support online.
Grassroots political site MoveOn.org was a focus for political campaigning during the election of the Democratic Presidential candidate and in the run up to the US election in November 2004. The site aims to encourage participation in political issues through practical organisation and has built an online community of around two million activists.
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