Furious Mansion chief negotiator David Kinsman has accused Manchester United of "double-dealing" after the Red Devils pulled the plug on a world record sponsorship deal.

At the request of United commercial director Andy Anson, Kinsman cut short business meetings in the Far East and flew into London on Friday believing negotiations were about to be concluded.

Instead, having been assured on Saturday there were no problems with discussions, Kinsman then took a call from Anson last night in which the United official admitted he had also been talking to another unnamed company and contact with Mansion was being terminated.

The news left Kinsman and the company's executives stunned. Kinsman claims Anson had verbally agreed a deal which would net United up to £70million over the next four years, all of which was in cash and a substantial portion in an up front payment.

"We are not naive businessmen by any stretch of the imagination but this has left us flabbergasted," admitted Kinsman, Mansion chief operating officer. "This might be the way Manchester United do business but it does not suit us.

"It was indicated to us that we had done a deal and I flew in from China for a meeting with Andy Anson to that effect. It was something of a surprise therefore to be told last night that United had been negotiating with someone else.

"During the negotiating process we had no idea this kind of double dealing was going on. Manchester United have not acted as we expected them to."

Kinsman confirmed that Anson had headed United's negotiating team and despite requests he had had no contact with any member of the Glazer family. However, Mansion did receive numerous emails from United fans requesting the gaming giant did not do business with the Glazers, whose £790million takeover of United has attracted such widespread controversy.

"We were concerned about that aspect of it because we like to think of ourselves as sponsoring not only the club but the fans as well," said Kinsman. "It did have an effect on us but we are businessmen and we needed to look after our own interests as well.

"Obviously the immediate reaction is one of disappointment but I have to say there are some members of our board who are quite relieved the deal has not gone through given what they have now found out about the people we were negotiating with."

Given the figures Mansion are talking about, it appears purely in financial terms United will not lose out following Vodafone's decision to terminate their £9million-a year deal two years early.

However, their reputation is being shredded - Mansion are not the first company to express their concerns about the club's negotiating policy. Korean electronics company LG accused the club of playing them off against other potential sponsors during their own negotiations.

Despite their shattering setback, Kinsman has vowed that Mansion will pursue sponsorship arrangements with other Premier League clubs with "an international fan base".

"We are not going to go away," he said. "We are a major player in the sporting arena and it fits our profile to be involved within the EPL. It is not a simple case of putting your name on a club shirt but I can tell you the alarm bells will start to ring if we find ourselves in this position again.

"We are very disappointed at the manner in which Manchester United have concluded these contract negotiations. We were very surprised the discussions were terminated in what we consider to be an unprofessional manner."

United said in a statement: "We would understand why anybody would be disappointed at not securing the shirt sponsorship deal for Manchester United. We have not and do not enter into periods of exclusive negotiation and every party we have discussed the shirt sponsorship with are aware of that.

"All the parties were aware that several discussions were going on at the same time and our priority is to look for the most appropriate deal for Manchester United. It's only the third time we have sold this property and clearly we want to get it right.

"We have been having discussions with Mansion, and we are sorry they feel that way and wish them every success in the future."