South Africa largest trade union, The Congress of South African Trade Unions (Cosatu), has come out fiercely against the proposed $4.2 billion takeover bid by Wal-Mart, the world's largest retailer for Massmart, South Africa's biggest food and general goods wholesaler.

Cosatu, comprising 21 trade unions, the biggest of the country's three main trade unions having over 1.8 million workers, is opposed to Wal-Mart's proposed transaction as it considers Massmart as one of the national companies of strategic importance.

Wal-Mart has one of the worst records on labour rights and continues to be hauled to courts by its employees, it noted.

"We call on urgent national action from government to investigate this hostile move by Walmart. Companies whose practice it is to abuse workers rights are not welcome in South Africa," Cosatu said in a statement put out on its website.

"We need a retail sector that creates decent work opportunities in this expanding sector, and the undermining of rights in one chain of stores will force non-compliance in other chains of stores and put our country on a downward spiral in terms of Labour Law compliance. Walmart is not welcome in the Western Cape."

Johannesburg-based Massmart, is one of the largest distributors of consumer goods on the African continent and is the leading African retailer of general merchandise, home improvement equipment and supplies.

The company runs 290 stores in 13 countries in Africa, with the vast majority of its stores in South Africa, and manages eight wholesale and retail chains operating under a variety of different brand names.

Historically, South Africa has always opposed any overseas firms from buying out large strategic companies unless the target company is in financial trouble.

It blocks large acquisitions under the Black Economic Empowerment (BEE) law that was introduced in June 2008 to give South Africans economic opportunities previously not available to them.

When Swiss miner Xstrata proposed a $68 billion merger of equals in 2009 with London-listed miner Anglo American, South African government said that it would oppose the merger under the BEE law.

Anglo American has large interest in South Africa and the government of South Africa felt that the merger would lead to job losses.

The South African government had also rejected the 2009 merger of India's Bharti Airtel with South Africa's largest mobile company MTN Group as it wanted MTN to maintain a separate identity.

Wal-Mart, the $408 billion retail giant and the world's largest public corporation by revenue, operates 4,081 stores in 14 countries outside the US, employing around 664,000 workers.

Although it is one of the largest employers in the US, Wal-Mart has a reputation for being the big corporation everyone loves to hate and is often compared to a 100 pound gorilla.

The company has been besieged with numerous labour problems, with accusations ranging from workers being denied overtime, bias over race, gender, age and disability, wage-and-hour claims to union busting.

Although the company maintains that these accusations are unfounded it has and continues to pay millions of dollars in settlements from lawsuits bought on by its employees against the company.

This is apart from the millions it spends every year trying to silence its critics through elaborate marketing plans.

The retailer's employees in the US have filed more than 250 suits related to labour law and anti-discrimination law in federal courts since January 2005. From 2005 to 2007, the courts in Pennsylvania and California have awarded Wal-Mart employees more than $251 million in pay and damage.

Investors of the company alarmed at such labour practices, had asked Wal-Mart in 2007 to form "special committee of independent directors'' to investigate the company's workplace policies amid a rising tide of employee lawsuits.

In June 2006, Norway's global pension fund, one of the world's largest, sold all its Wal-Mart shares on serious and systemic violations of human rights and labor rights.

The fund sold holdings worth $2.5 billion kroner ($398 million) in December 2005 in Wal-Mart and Wal-Mart de Mexico in December 2005.