By Oliver Brett

Klusener and Boje, once of South Africa, now Northants team-mates

The England and Wales Cricket Board is to examine "as a matter of urgency" the invasion of South African players in county cricket.

On Tuesday, a Championship game between Northants and Leicestershire featured five South Africans on each side.

All but one are signed under a law which allows workers from countries with associate trade agreements with the EU to have equal employment rights.

"There is great concern about what is happening," said an ECB source.

"The board will look at the situation of an almost doubling of non-English qualified players as a matter of urgency."

The EU loophole - known as the "Kolpak" ruling - directly accounts for the massive influx of South Africans in county cricket since 2004.

Many of them have grown disenchanted with racial quotas in their own country and are keen to seek opportunities in England.

Counties are allowed to field only one official overseas player per match, but it has not been possible to enforce a limit on Kolpak players.

606: DEBATE Today Northants have five South Africans. Surely this is completely wrong and very damaging for prospective English-born players RIVERWALK

The money is docked from the �1m handout granted by the ECB to each county every year.

Explaining the system, an ECB spokesman told BBC Sport: "The ECB policy is quite straightforward.

"We encourage the selection of as many England-qualified players as possible."

But the scheme does not appear to have worked, with some counties apparently showing little interest in maximising their potential income from the ECB.

Northants had five South African Kolpakkers on their books until late March, when they offered a sixth, Johann Louw, an overseas contract in late March.

Leicestershire chairman Neil Davidson says he remains committed to helping produce future English Test cricketers.

He said last October that counties should be required to play a minimum of four English-qualified players aged 25 or under in the Championship.

THE KOLPAK RULING Maros Kolpak was a Slovakian who won a restraint of trade case against the German Handball Federation at the European Court of Justice in 2003 Slovakia did not join the European Union until 2004 - but Kolpak won the right to not be considered as an overseas player, as his country had an associate agreement with the EU The Kolpak ruling gives such players the same rights as an EU worker As a result, many South Africans, Zimbabweans and West Indians have been able to play county cricket in England without a work permit - and not be classed as overseas players

And he suggested incentives for giving opportunities to English cricketers from younger age groups.

Davidson added: "It is strongly rumoured that Australia and New Zealand will shortly sign trade agreements with the EU similar to the West Indies.

"In that case players from four of the major Test playing countries will then be legally entitled to work here under the Kolpak judgement."

But although it caps the number of official overseas players at one, the ECB has not yet found a legal way of enforcing counties to field a minimum number of English-qualified players.

It also has to tread extremely carefully, with European employment legislation notoriously difficult to combat.

The ECB lost one legal case on 30 April, when Andrew Hall, Justin Kemp and Johan van der Wath were cleared to play in county cricket after winning appeals.

The three South Africans had initially been refused registration after competing in the unauthorised Indian Cricket League.

On Tuesday, Leicestershire fielded five South Africans, four Englishmen, a West Indian Kolpakker and an Australian with a UK passport.

In addition to their own South African quintet, Northants had five Englishmen and an Irishman.