Manchester United insist Real Madrid were the ones to blame for the shock 11th-hour collapse of David de Gea's proposed move to the Bernabeu.

United and Madrid had agreed a deal worth £29million for the sale of the Spanish goalkeeper on Monday, with Keylor Navas coming to Old Trafford as part of the agreement.

But shortly after the 11pm deadline for European transfers it emerged the necessary paperwork had not been lodged in time and the deal had therefore fallen through.

There was no sign of De Gea's name, nor that of Navas, on a confirmed list of La Liga transfers, which was published after the deadline had passed.

United insist they uploaded the requisite documents to FIFA's Transfer Matching System before Monday's 11pm deadline (BST).

Sources at Old Trafford have rejected reports in Spain that they submitted their paperwork after the deadline and claim they have a time-stamp from FIFA as proof.

It is understood that United feel it was Madrid who failed to file their paperwork in time and believe they must take the blame for the deal's collapse. Reports in Spain indicated the documents did not reach the Spanish league office until 28 minutes after the deadline.

Although Madrid retain a glimmer of hope that the deal will somehow go through, there have never been any successful appeals regarding late transfers in the league's history.

In February this year, Levante lost an attempt to overturn a ruling that canceled their loan bid for Fulham's Bryan Ruiz because they had missed the deadline for submission.

Quite why Madrid left it so late to try to secure De Gea's signature is a source of debate among the powers that be at Old Trafford.

Madrid made De Gea their number one target earlier this summer following the departure of Iker Casillas to Porto and the two-time United player of the year himself was determined to complete the move too.

The 24-year-old, who joined United from Real's neighbors Atletico Madrid four years ago, hails from the Spanish capital and his pop star girlfriend Edurne Garcia also lives in the city.

But it was not until the final day of the window that Madrid made their first significant bid for the player, and that was too late to get the deal over the line.

The United board are said to be "relaxed" about the situation.

Although De Gea is yet to play for the club this season, United know they will now have a world-class goalkeeper to choose, should he be deemed mentally fit enough to play in Louis van Gaal's eyes.

The United manager will be hoping to wrap up his £36million move for Monaco striker Anthony Martial before the Premier League transfer window shuts at 6pm on Tuesday.

More incomings and outgoings are expected. United have received offers for defender Marcos Rojo, but he wants to stay.

Young striker James Wilson could go out on loan.

Adnan Januzaj was the first out of the door on Monday, joining Borussia Dortmund on a season-long loan.

He was closely followed by Javier Hernandez, who signed for Bayer Leverkusen for 10 million euros (£7.3million). Anders Lindegaard became the third United player to leave on Monday when he signed for West Brom on a free transfer.

FIFA is understood to be looking into the details surrounding the collapsed transfer but it would be up to Real Madrid to make an appeal as it is the Spanish transfer window which has closed.

The only grounds for a successful appeal would be if the club could prove there was a failure in the administration involving the Spanish authorities.

FIFA would not give any specific details on an appeal however.

A FIFA spokesman said: "The information in the International Transfer Matching System (ITMS) is confidential to the registered users of ITMS and we are therefore not in a position to give information on transfers.

"We would suggest that you contact the respective clubs directly for additional information on the paperwork topic and the potential filing of an appeal to FIFA on the matter."