THE FORMER administrative secretary of the Northern League, which became one of Italy's biggest parties on the wave of revulsion against corruption and misgovernment, was arrested yesterday. Alessandro Patelli is suspected of receiving illicit donations for the movement - a charge levelled at scores of politicians from the old discredited parties the League wants to replace - and falsifying accounts. He was not charged with the more serious crime of corruption.

The arrest was a severe blow for the League, for which honesty and good government are a vital part of its platform. It came at a bad moment: the League has just lost municipal elections in the northern ports of Genoa, Venice and Trieste and dissent is rising in its ranks over Umberto Bossi's leadership.

The arrest followed an alleged admission by Carlo Sama, former chief executive of the huge Montedison chemicals concern, that the company illegally passed 200m lire (pounds 80,000) to the League for the 1992 election. Mr Sama is also said to have told Milan's chief corruption investigator that Montedison gave money to other parties; some newspapers have named leaders of the former Communist party - the principal victor in the municipal elections - as recipients. But the magistrates have not commented.

Mr Bossi's first reaction was uncharacteristically restrained. 'We have always had confidence in the judiciary . . . and we urge (it) to act quickly and release those who are innocent, like Patelli.' Marco Formentini, the League mayor of Milan, voiced the suspicions of many, saying: 'I personally believe that Patelli has been unjustly named by someone who has an interest in muddying the waters.'

The campaign for general elections next year has begun and anything that might besmirch the image of the opposition parties, particularly the former Communists and the League, which stand to replace the old political class, will be seen as a plot to discredit them.