Political row a turn-off for viewers of news bulletins and a switch-on for debate and analysis shows.

While the scandal over MPs’ expenses has been catastrophic for Parliament, the opposite has been true for debate and news analysis shows as the revelations boosted ratings.

The runaway beneficiary was BBC1’s long-running political debate show, Question Time, hosted by David Dimbleby, which first aired in 1979. The panellists, including housing and planning minister Margaret Beckett, were heckled by members of the audience as the public furore surrounding the issue gave the programme its largest audience since April 2005.

The hour-long show on 14 May, in its late-night slot of 10.40pm, averaged an impressive 3.8 million/29.5%, hitting a peak of 4 million/29.5% at 10.55pm. The show was up by 46% compared with the channel’s year to date slot average of 2.6 million/20.7%.

The show has also been a hit online. A YouTube clip featuring Beckett had been viewed 125,000 times by Friday afternoon.

The last time Question Time got a higher audience in its regular 10.40pm slot was 21 February 2002 when 4.8 million (31.2%) tuned in.

Viewer interest in MP’s ex-pens-es was sustained after Question Time ended at 11.40pm with BBC1’s This Week, which looks at events in Westminster. The 35-minute show, featuring Andrew Neil, Michael Portillo and MP Diane Abbott, attracted 1.5 million/23%. It was the programme’s best performance since 24 June 2004 when 1.8 million/24.6% watched.

BBC2’s Newsnight gained a more modest boost. The current affairs show averaged 958,000/7.6% in its regular 10.30pm slot. The week’s audience was up by 12,000 on the programme’s performance so far this year of 946,000/6.6%.

While news analysis/debate-style shows have benefited from the scandal, it appears to have been a turn-off for viewers of news bulletins. The main news bulletins on the two biggest terrestrials channels actually saw audiences fall, even though both BBC1 and ITV1 covered the issue in depth.

BBC1’s Six O’Clock News averaged 4.1 million/24.9% last week, a fall of 700,000 on the bulletin’s average year-to-date performance of 4.8 million/26.3%.

The Ten O’Clock News showed a smaller decrease. Last week, the programme averaged 4.7 million/24.5% compared with a year-to-date performance of 4.9 million/24.9%.

Similarly, ITV1’s key news programmes also had a fall in viewer numbers last week. Its Evening News at 6.30pm averaged 3.3 million/18.4% across Monday to Friday. This compares with a performance of 3.7 million/18.8% for the year so far. The 35-minute News at Ten averaged 2.2 million, 11.5% share down from its year to date average of 2.5 million/12.6%.

Elsewhere, Channel 4 News wasn’t immune from a drop in viewers. Its main 7pm show averaged 863,000/4.5% (including viewers for C4+1) across last week. This compares with a programme average so far this year of 910,000/4.3%.

Politically themed shows may continue to benefit. With the resignation of the Speaker of the House of Commons, the saga of MP’s expenses looks set to rumble on.