Controversial clamper Daniel Clout is being investigated by the New Zealand Security Association after "numerous" complaints from disgruntled drivers.

"Under the New Zealand law for security guards and private investigators you must hold a current certificate of approval issued by the Ministry of Justice and he doesn't hold any of those," association chairwoman Bronwyn Paul said yesterday.

Mr Clout, who trades as Egmont Security, continues to be the focus of allegations of over-zealousness.

This week three delivery drivers say he clamped them within seconds of them leaving their vehicles.

Mr Clout, who has been in the spotlight for clamping an unmarked police car and a scuffle with district councillor Andrew Judd, could not be found at any of his usual haunts yesterday and did not return calls.

Ms Paul said the investigation began after the organisation received numerous complaints about Mr Clout.

She said while Mr Clout was providing a service, he had to work within certain protocols.

"I would not expect that the way he is acting is within those boundaries."

Illegal clampers can incur fines of up to $40,000 for individuals and $60,000 for companies.

Courier driver Donna Breach said her van was clamped, in a private car park in King St, within seconds of her relief driver getting out to make a delivery on Monday.

"About a minute, not even a minute, in and out, so probably 40 seconds," Ms Breach said.

She said Mr Clout was not wearing a uniform, would not produce any official identification and was illegally parked himself.

The driver Matt Weir, of NZ Couriers, said he had been away from his van, which had the hazard lights on and the engine running, for less than two minutes.

"I got out, ran to Judd Opticians to deliver one parcel and came out and both wheels had been clamped," Mr Weir said.

Another delivery driver, Bernie Mascull, said he was only out of his car for about 30 seconds on Tuesday when Mr Clout pounced.

Mr Clout signed up to a voluntary code of conduct for the industry, which came into force on October 1. The code gives motorists 10 minutes' grace before being clamped, and requires clamping staff to wear uniforms and carry official identification.

However, Consumer Affairs Minister Simon Bridges said Mr Clout withdrew from the code while he appealed his conviction for assaulting a German tourist whose van he clamped in March.

"As you are aware, Mr Clout of Egmont Security has been found guilty of assault, which means he cannot maintain a security licence or fully comply with the code of conduct for wheel clamping on private land," Mr Bridges said.