Westwood, who has filmed seven series of Rogue Traders, added: "In times of recession people set up landscaping businesses by buying a second-hand van and a barrowful of tools and away they go. Landscaping is one of the easiest trades to set up in, but not one of the easiest to do well.
"The risks are that people will have a duff job done. A good or bad job may look almost the same until a couple of months later, particularly with hard landscaping when the sub-base goes.
"I do a lot of adjudication work where jobs have gone wrong, as an expert witness. In the past five years, that has gone from five to 20 per cent of my work. I'm not sure if that's because contractors have got worse or because the public are more aware of their rights."
Westwood would not go as far as to call for licensing for all landscapers: "There are so many areas, from the Chelsea show down to jobbing gardeners who fulfil a role by weeding Mrs Miggins' flowerbeds and not charging £30 an hour.
"People should have NVQs but unfortunately [members of] the public often don't recognise them."
Westwood said those who knock trade associations are further eroding standards: "With all trade associations, only the good guys are going to join. Guys who are going to do a quick, cheap job - why are they going to join? I'm all for trade associations. They give clients more confidence. Contractors are vetted and not just sending in £10 and getting a sticker for the van."
Westwood Solutions has just finished a design and build for the St John's Ambulance memorial garden at the National Memorial Arboretum in Staffordshire.
Westwood has also completed a front garden in Wales for Moneysupermarket.com founder Simon Nixon. Westwood said: "He's not struggling in the recession."
BALI chief executive Sandra Loton-Jones said: "When times are harder than normal, members find they are not getting the jobs they are tendering for or hoping to get, particularly on the domestic side.
"Our members' contracts are as keen as they can be and they get increasingly frustrated when they find the work they hoped to get has been taken by people who are not VAT registered and not fully aware of the legislative position. The world has changed so much - with Work at Height Regulations, for instance, that are not just affecting tree work. You have to adapt work practices to conform to legislation.
"These people devalue the industry and make it look like something anyone can turn to."
Association of Professional Landscapers chief executive Jason Lock said: "My overriding concern is that there is the temptation in tight economic times to price a contract short to win the work.
"In these instances, nobody wins. The contractor makes no money and invariably has to cut corners and the client is short-changed with substandard work. It may be a short-term fix but in the long term it will affect their reputation."
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