The Congress of South Africa Trade Unions (Cosatu) will lose more than R1-million a month in affiliation fees after its central executive committee (CEC) decided to expel the National Union of Metalworkers of South Africa (Numsa).

"The only thing we did – in order to be a member in good standing in Cosatu – was to pay an affiliation fee," Numsa treasurer Mphumzi Maqungo said on Tuesday.

Numsa's estimate of R1 022 000 a month was based on a R2.92 affiliation fee from each of its estimated 350 000 members.

This meant Cosatu could lose R12 264 000 a year without Numsa.

Numsa also paid R38 000 towards the shop steward magazine, Maqungo said.

Cosatu spokesperson Patrick Craven said the issue of finances was "a matter that Cosatu is still looking at".

The Cosatu CEC decided to expel Numsa at meeting which ran into the early hours of Saturday morning.

During the meeting Numsa presented its argument to Cosatu on why it should not be expelled, but this did not stop its ousting by 33 votes to 24.

Numsa has been at loggerheads with Cosatu since the trade union federation's general secretary Zwelinzima Vavi was suspended last year for having an affair with a junior employee.

She originally claimed he had raped her but did not press charges with the police. Numsa took Cosatu to court to reverse the suspension, where it won its bid and Vavi returned to work.

Numsa held a special national congress in December where it resolved not to support its traditional ally, the African National Congress, in the general elections.

The union has also called for Cosatu to hold a special national congress.

Labour analyst Terry Bell said Numsa had not been expelled from Cosatu.

"The CEC has expelled Numsa, but such a decision has to be ratified – and may be overturned – by a national congress (special or otherwise). The CEC decision therefore has the effect of a recommendation."

Cosatu deputy general secretary Bheki Ntshalintshali said at a briefing on Tuesday that the decision to expel Numsa was a CEC decision and was binding on all the structures of the federation and its leaders.

"All [are] expected to observe it without exception," he said.

Ntshalintshali said Numsa was advised that it could appeal against its expulsion, to Cosatu's national congress.

The next national congress is expected to be held in September next year.

Bell said Cosatu affiliate, the National Union of Mineworkers (NUM) was probably the biggest contributor to the trade union federation's coffers prior to Marikana.

Forty-four people died in strike-related unrest at Lonmin's platinum mining operations in Marikana, North West, in August 2012.

Thirty-four people, mostly striking mineworkers, were shot dead in a clash with police on August 16, 2012. More than 70 people were wounded and more than 200 were arrested. The police were apparently trying to disarm and disperse them.

In the preceding week, 10 people, including two police officers and two Lonmin security officers, were killed.

Subsequently, a large number of NUM members joined the Association of Mineworkers and Construction Union (Amcu).

This led to Amcu being recognised as the majority union at Lonmin over NUM.

Bell said it was unknown how NUM's figures had adjusted post-Marikana, but the union still listed its membership figures at the "historic" 270 536.

Seven other Cosatu affiliates, the Food and Allied Workers Union, the Democratic Nurses Organisation of South Africa (Denosa), the South African Commercial Clothing and Allied Workers Union (Saccawu), the Communication Workers Union (CWU), the South African State and Allied Workers Union, the Public and Allied Workers Union of South Africa and the South African Football Players Union have all stood by Numsa and vowed to fight the expulsion.

The South African Municipal Workers Union (Samwu) has also previously stood with the other unions, but is currently embroiled in its own legal battle over expulsions in the union.

Numsa deputy general secretary Karl Cloete said at a briefing on Wednesday last week that he had not received anything from Samwu to say it was not supporting them.

When asked on the potential loss in membership fees to Cosatu if the other pro-Numsa unions were no longer in Cosatu as well, Bell said only Denosa, CWU and Saccawu had substantial memberships.

"But if their contributions are added together, it would probably amount to no less than about R3-million a month."

In terms of investments, the metalworkers union has its own Numsa Investment Company, while Cosatu has Kopano Ke Matla investment arm.

Maqungo said Numsa has only invested through its company.

"We have got our own investments as Numsa. There are no investments through them [Cosatu]."

Ntshalintshali said on Tuesday that the Cosatu constitution was "quite clear" about claims by members on the trade union federation's investments.

"The constitution is quite clear, its says because it is a collective it [the investment] belongs to the federation," he said.

"Equally it answers the question over what happens when you wind-up a federation, what happens to its assets, do you distribute among members... can anyone have a claim?

"It [the constitution] says no. The federation as a whole has to decide over where to donate whatever you may have in terms of the assets... it is a constitutional requirement -- it is not a question about getting dividends."

Bell said the investment area was "terribly opaque".

"But because these companies are, basically, at arm's length from the federation/unions involved and are subject to rules governing investment companies, shareholders (be they unions or individuals) cannot really be disadvantaged for political reasons," he said.