Advertising watchdogs are investigating a mailshot from a rail operator that included a fake parking ticket.

Rail operator Midland Mainline has apologised after sending the "mock" London parking tickets to 50,000 customers in the East Midlands.

It has received complaints from customers who believed them to be genuine.

The tickets were posted in a clear plastic envelope that said "Parking Offence Notice City of London".

Apology offered

One recipient complained to Trading Standards officials who said they would investigate the mailshot.

At the bottom of the notice is a line that says the ticket is a promotional leaflet for Midland Mainline, and the company's logo is on the back of the address label.

Midland Mainline has apologised for the confusion and any upset caused by the promotion.

One recipient said the �30 mock fine "scared me half to death".

We would like to apologise to anyone who was annoyed or confused by this

James Burles Midland Mainline

"If you read the small print it says you can do two things: Explode with rage or take the train," she told BBC Radio Nottingham.

"I think it is appalling. Some people will be more worried than me and it might give them a heart attack."

Another recipient said: "The initial feeling I had was one of panic."

"I was really disgusted."

The Advertising Standards Authority is investigating the mail-out to see if it is misleading.

Midland Mainline's head of marketing James Burles said: "We would like to apologise to anyone who was annoyed or confused by this.

"We wanted to produce something that was different and stood out from other bumf that comes to people's doors."