Currently one of the largest privately owned confectionery companies in the world, Mars reportedly told workers that production of its Twix confectionery brand will soon be outsourced to France and Germany, while production of Starburst-branded confectionery will be transferred to the Czech Republic.
Its eponymous best-selling brand, however, will still be produced in the UK, alongside Maltesers and Snickers, at its second site in Dundee Road, Slough - although this has so far failed to appease trade unions.
"The company made £140 million last year and just wants to make more. The managers have also been given huge pay increases. It is sick," Frank Loveday, regional officer of the Bakers, Food and Allied Workers' Union commented.
The union confirmed that around five hundred jobs will be slashed by the end of the year at Mars' Slough production facility (unless some workers opt for voluntary redundancy), while a further two hundred will be spread out across its sites in Leicestershire, Peterborough, Kings Lynn and Leeds.
In keeping with its long-standing tradition of privacy, Mars has so far refused to comment, although is expected to make a statement later today.
The company joins a host of other leading international confectionery manufacturers, including Nestlé, Cadbury and Kraft, which have all recently opted to downsize their British workforces.
In April last year, for instance, leading global food producer Kraft announced the closure of its York production facility - a move that will see the production of its Terry's Chocolate Orange, Terry's All Gold and Twilight brands transferred to alternative sites across Sweden, Belgium, Poland and Slovakia later in the year.
According to industry analysts Euromonitor International, Mars was western Europe's sixth biggest confectionery brand in 2003, accounting for 1.4 per cent of all retail sales. Conversely, its Snickers and Twix brands ranked just outside the top ten, notching up respective retail sales of 1 and 0.9 per cent.
In the UK, however, its Mars brand enjoys a slightly larger market share - second only to Cadbury's Dairy Milk brand and this, together with its Galaxy and Maltesers brands, account for 8.1 per cent of UK retail sales of branded chocolate confectionery.
Mars' traditional strategy, which last year helped rack up an estimated turnover of £9.6 billion (€13.8 billion), has recently drawn criticism from analysts for its heavy reliance on the chocolate confectionery segment - currently one of the slowest growing confectionery sectors in western Europe.