Committee on Standards in Public Life chairman Sir Alastair Graham told PRWeek the committee's research flagged up a 'serious lack of trust' in government.
He said falling trust 'leads to a much lower turnout. The likelihood is turnout among the over-50s will be very high, but among young people it is likely to be well below 50 per cent. There is a general expectation that turnout will be below that of the last election'.
Turnout in the 2001 election was 59 per cent - the lowest since 1918.
But Graham said there was still time for the Government to boost turnout if it tried to 'engage the electorate' by being more open.
He added that comms professionals could 'advise how best to limit damage, but they can also say: "You might be surprised by the positive response if you are honest"'.
The Joseph Rowntree Charitable and Reform Trusts established the Power Commission last November to examine how to encourage greater electoral participation.
Chaired by Helena Kennedy QC, it has heard evidence from Conservative leader Michael Howard and former leader of the House of Commons Robin Cook and reports in early 2006.
MORI research in December revealed only 52 per cent of respondents were 'absolutely certain' to vote at an immediate general election.