PARKING wardens starting a seven-day strike yesterday were boosted by a “solid” walk-out from colleagues monitoring CCTV cameras.

Enforcement contractor NSL pays staff in the north London Borough of Camden 23 pence below the London living wage of £9.15 an hour.

The firm is controlled by private equity giant AAC Capital Partners and has refused to negotiate on demands for adequate sick pay and a shorter working week.

Public-sector union Unison called for Camden Council, which is an accredited living wage employer, to take the contract back in-house and for NSL to face “financial penalties” in the meantime.

“These workers face daily abuse, often overtly racist, and even when physically attacked on the job there is no guarantee that they will automatically get occupational sick pay,” said Camden Unison branch secretary George Binette.

Pay rates vary dramatically on London’s outsourced parking contracts, with some civil enforcement officers making below £8 an hour.

But unionised NSL employees in Kensington and Chelsea get a minimum of £9.31 an hour, while in Ealing the basic rate is £9.73 and in Waltham Forest over £11.

As the week-long walkout kicked off yesterday, reps reported strong turnout, with a lack of office-based staff compromising the borough’s CCTV-based parking enforcement operation.

Camden Unison’s dispute is its second in three years. In 2012 workers settled for just above the rate at which the living wage was then set.

NSL’s 2014 turnover exceeded £200 million, with reported profits of £18.8m. Last year the firm generated around £24m of revenue for Camden council.