NEW DELHI (Reuters) - India’s main opposition Congress party will simplify the goods and services tax (GST) and take “rational economic decisions” to attract foreign investment if voted back to power in a general election due by May, its leader Rahul Gandhi said on Saturday.

FILE PHOTO: Rahul Gandhi, President of India's main opposition Congress party, speaks during a news conference at his party's headquarters in New Delhi, India, December 11, 2018. REUTERS/Anushree Fadnavis/File Photo

Launched in 2017, the GST was initially hailed as Prime Minister Narendra Modi’s biggest economic reform as it replaced more than a dozen federal and state levies and unified Asia’s third largest economy.

But its chaotic implementation and complexities here -- months after a shock ban by Modi on high value bank currency aimed at unearthing untaxed wealth -- badly hurt small businesses and led to millions of job losses in the cash-driven economy, presenting the biggest challenge to Modi's re-election chances.

Gandhi, scion of India’s Nehru-Gandhi dynasty, said during a visit to Dubai that foreign investment was at a multi-year low in India due to the “ill-advised and badly thought out economic moves” such as the currency ban and a “poorly designed GST”.

“We will take some rational economic decisions,” he told a press conference, which was broadcast live on Twitter. “We will restructure the GST and we will embrace investments from the Middle East and other parts of the world. We are the party of (India’s economic) liberalization, we are the party that gave the fastest economic growth in the first decade of the century, and will do that again.”

He said his main priority would be to create jobs, simplify the GST, rebuild confidence in institutions such as the Reserve Bank of India -- whose governor resigned recently after a fight over autonomy with the government, and the Supreme Court.

Four Supreme Court judges held a rare press conference early last year saying that “unless this institution is preserved and it maintains its equanimity, democracy will not survive in this country”.

Modi told a BJP convention in New Delhi on Saturday that for Congress “every institution was wrong and only they were right”.

The Congress press conference was organized by the Indian Overseas Congress, which is present in about 35 countries, as Gandhi tries to reach out to rich Indians living abroad for funds and social media support for the party that has dominated the country’s politics for decades before being nearly decimated in the last general election in 2014 by Modi.

But back home, Gandhi received a jolt when bitter rivals Bahujan Samaj Party (BSP) and the Samajwadi Party (SP) announced an election tie-up here without Congress in Uttar Pradesh state, which sends the highest number of lawmakers to the lower house of parliament.

“The BSP and SP have made a political decision,” Gandhi said. “It’s on us on how to strengthen the Congress party in Uttar Pradesh and we will fight with our full capacity. Whether we do or their alliance does, the BJP is not winning there.”

Modi said at the Delhi convention that the opposition was working on a “desperate alliance”, while the BJP would give a “strong government”.

The Hindu nationalist BJP lost power in three key states recently, forcing the government to announce a flurry of measures to woo small businesses and the less well-off since then.