Market Report: Bookmakers downgraded as a result of clampdown on fixed-odds betting machines

It looks as if the bookies may be playing in the last-chance saloon when it comes to fixed-odds betting machines, the so-called "crack cocaine" of gambling.

Bookmakers are facing a clampdown on the highly lucrative machines, which can take up to £300 a minute, after David Cameron pledged to "get to grips" with the issue.

While a Labour motion brought to give local authorities greater control over the machines was defeated, some form of action seems increasingly likely.

In the wake of the Prime Minister's comments, Barclays issued a note downgrading Ladbrokes, off 15.6p to 164.1p, and William Hill, down 28.7p at 371.1p.

African-focused Tullow Oil was one of the biggest risers on the benchmark index, up 25p to 845p, after a positive note from HSBC and speculation that it could be a bid target for Norway's Statoil.

The building materials group CRH also made gains after an enthusiastic upgrade from UBS. The broker reckons that "continued recovery in the US and early signs of improvement in Europe should help CRH deliver its first earnings growth in eight years". CRH put on 38p to 1,625p.

The benchmark index as a whole was pulled lower by retailers, closing down 30.44 points at 6,691.34.

Dour trading updates from Morrisons and Tesco spooked investors and sent both tumbling. Morrisons was off 19.7p at 234.5p while Tesco lost 3.95p to 324.35p.

One surprise winner was Marks & Spencer. Despite releasing a disappointing set of results, the high street stalwart shot to the top of the FTSE 100, helped by an upgrade from Investec. M&S added 16p to 460.9p.

On the midcap index a bullish update from the wireless technology and antennae producer Laird sent shares soaring over 10 per cent. The company said it was confident of meeting full-year revenue expectations, reaffirmed its dividend commitment and announced Asian expansion plans. Laird added 34.3p to 317.1p.

It was a different story for the telecoms testing firm Spirent, whose shares collapsed after it warned that full-year revenue would be 14 per cent lower than last year due to delays in the US. Spirent was down 13.45p to 85.9p.