By Sonia Mathur, India Correspondent

The Indian elections this year are likely to be the biggest in world history. From April 7 till May 12, some 815 million eligible voters, the populations of the EU and US combined, will flock to polling stations and cast their vote.

They will be voting to choose their representatives for the lower house of the Indian Parliament – the Lok Sabha.

They will have plenty of choice. India is a multi-party democracy. There are six national parties, 47 state parties and 1563 smaller, “unrecognised” parties. In fact there are a total of 1,616 registered political parties in this year’s elections.

Over the last thirty or so years, two of the six national parties have emerged as the main contenders for the top job. The Congress, which has ruled independent India for 54 out of 67 years, and the right-leaning Bharitya Janata Party (BJP). These two form pre and post-election alliances with regional parties to form governments.

The regional or state parties hold little sway outside their heartlands, but trade support with the main parties for their own local needs.

For example, the Dravida Munnetra Kazhagam, or DMK, in Tamil Nadu trades support for a national party in Delhi in order to get preference over the neighbouring state of Kerala for control of its water supplies.

Manmohan Singh has been the prime minister of the country for a decade now. He belongs to the Congress party, who are in alliance with a lot of regional parties, including the DMK, and form the ruling United Progressive Alliance, or UPA.

As the world’s largest democracy goes to the polls this month, the UPA will take on the BJP-led NDA or National Democratic Alliance.

The NDA were last in power from 1998-2004. Its prime ministerial candidate this time is the controversial chief minister of the Indian state of Gujarat, Narendra Modi. A populist with humble origins, Modi is credited with bringing prosperity and growth in the state of Gujarat, but his critics argue he is divisive, with extremist views.

Modi’s economic policy is based on urbanisation and industrialisation. He wants the Indian economy to grow at a rate of ten per cent per year. India’s growth has slowed in the last two years to half that – which is a ten year low.

Modi says he wants to invest in infrastructure, skills and manufacturing; to create a country that creates its own wealth by encouraging entrepreneurship, though he hasn’t detailed exactly how he’s planning to achieve this.

The Congress party-led UPA is pushing popular welfare measures. For many years its focus has been on hand-outs, such as subsidies on fuel and food, but many feel these policies have taken funds away from investment and growth.

Welsh investors and exporters looking to do business with India would probably prefer the BJP-led alliance in the centre. The markets in India have reacted positively to the polls showing a lead for the NDA. After all, Narendra Modi has successfully attracted millions of pounds of foreign investment into Gujarat as the chief minister.

His main focus also seems to be on spurring growth with private sector jobs and investment. However, he and his party have opposed foreign retail investment. The BJP hasn’t been keen on allowing the likes of Wal-Mart or Tesco in India, mostly because its core supporters are smaller shopkeepers and retailers.

“Barring the multi-brand retail sector, FDI (foreign direct investment) will be allowed in sectors wherever needed for job and asset creation, infrastructure and acquisition of niche technology and specialised expertise. BJP is committed to protecting the interest of small and medium retailers,” the party said in its manifesto.

In an attempt to boost its economic performance, the Congress-led UPA government imposed duties on gold imports to try to cut the trade deficit. In an effort to rein in inflation, the central bank has raised interest rates three times since September. The government has also approved several infrastructure projects that had been stuck in bureaucratic bottlenecks.

However, in its ten years in power, the ruling UPA has been hit by scandals and controversies, such as the allegations of wrongdoing and corruption in the holding of the Commonwealth Games.

The alleged illegitimate wealth created by some top officials of the Commonwealth Games Organising Committee through over-reporting of Games costs is being investigated by the Central Vigilance Commission as well as the Central Bureau of Investigation (CBI).

The allegations of corruption over allocation of 2G contracts in 2008 led to the then minister for telecom, A. Raja, being arrested and taken into custody. In 2011, Time magazine listed the scam at number two on their “Top 10 Abuses of Power” list, just behind Watergate.

In an attempt keep those involved in the scandals away from the elections, the Congress party is pushing Rahul Gandhi on posters and on the campaign trail. He’s the latest offering from the Nehru-Gandhi dynasty that has dominated Indian politics since independence. Party bosses hope another Gandhi name on the ticket will help smooth over the inevitable disappointments of incumbency.

And Congress may be right to worry. The polls show a lead for the BJP, perhaps chiefly because there seems to be a palpable need for change among voters in India. But there are still concerns that the BJP hasn’t given any details on its economic agenda, and its associations with Hindu extremists means the party struggles to capture the sizeable Muslim vote in India.

But polls in India are, perhaps unsurprisingly, often off the mark. As the saying goes – the only thing predictable about the Indian elections is that they’re highly unpredictable.