Manchester United are adding as many as 24,000 fans on to crowd attendances compared with the actual number of people watching games at Old Trafford, according to police data.

Sir Alex Ferguson's team have not had a single crowd over 70,000 for a league match, police say, not taking in Monday's game against Manchester City. The club, in contrast, recorded attendances in excess of 75,000 every time. Instead Greater Manchester police's figures claim the average crowd for league matches, excluding City, is 10,000 below what the club say. The police records state it is 65,601 rather than the official figure of 75,527. In all competitions it is 61,739 rather than the club's 73,653.

United are still the best-supported club in England by some distance but the new set of figures claim Old Trafford was not even half-full for the Capital One Cup tie against Newcastle in September. The police recorded the number of people who passed through the turnstiles at 33,409. United gave the crowd as 46,358. In the next round, against West Ham, the disparity was even bigger. The police put down the crowd as 51,724, whereas United recorded it as 71,081.

When United played Cluj in the Champions League in December, having qualified for the knockout stages, the crowd was announced as 71,521. In fact, the police say it was 46,894.

The disparity is because United, in common with other clubs, release the number of people who bought tickets, whether or not they attend. The police keep their own record of actual match-goers for safety purposes and have released the data to the Redsaway fans' website under the Freedom of Information Act.

The figures show the high number of supporters who will buy tickets for matches without going. Arsenal are among the clubs who suffer the same problem on a large scale.

United's largest crowd of the season for a league match, according to the police, was 69,933 for Liverpool's visit in January (the club put it at 75,501). The lowest was against Southampton later that month. On that occasion the official attendance was given at 75,600 when, according to the police, the genuine figure was 59,766. In other words, almost 16,000 ticket-holders stayed away.

The Real Madrid match in the Champions League attracted the one 70,000-plus attendance at Old Trafford this season, in the data. The police recorded it at 72,299 whereas United declared it was 74,959, lower than any domestic league match because of Uefa's seating restrictions.