The campaign logo, tagline and theme song will feature in all the advertisements, posters, radio jingles and billboards of the Congress and the ruling Bharatiya Janata Party (BJP).

The focus of Congress' "Ab Hoga Nyay" (now, there will be justice) remains on "Nyay", the acronym for its minimum income guarantee scheme -- Nyuntam Aay Yojana -- under which the party has promised to give Rs 72,000 per year to 20 per cent of the poorest families if the party is voted to power.

The Congress slogan is based on the positive feedback the party received around the concept of 'Nyay', sources said.

"We are seeking justice or 'Nyay' against the injustices committed in the past four years. Those who promised 'Acche Din' only delivered 'Anyay' (injustice)," said Anand Sharma, Chairman of the Congress Publicity Committee.

Keeping Congress President Rahul Gandhi at the heart of its campaign, the visual elements include his interactions with people from all walks of life over the past few years.

"Simplicity, genuineness and honesty as opposed to hollow, empty slogans and fake promises is the approach the Congress publicity campaign takes," Sharma said.

Advertising agency Percept will work on the creative aspects of the Congress campaign, including a video jingle penned by Javed Akhtar and directed by filmmaker Nikhil Advani.

The campaign will focus on justice for the poor, unemployed youth, farmers, women, dalits, tribals and businessmen hit by the Goods and Services Tax (GST), the party said.

The Congress will also deploy large container trucks painted with the slogan "Ab Hoga Nyay" which will travel across the country.

Meanwhile, Finance Minister Arun Jaitley on Sunday launched the BJP's campaign themes with the main slogan being "Phir Ek Baar Modi Sarkar" (Modi government once more).

"The first theme of our campaign will be 'Kaam Karne Waali Sarkaar' (a government that works). Our second theme will be 'Imaandar Sarkaar' (honest government). The third theme will be 'Bade Faisle Lene Waali Sarkaar' (government that takes big decisions)," Jaitley said, adding that the sub-themes would combine the larger theme of "Phir Ek Baar Modi Sarkar".

Unveiling the party's campaign materials, he said the BJP's campaign themes will talk about honest governance, ability to take major decisions, women's empowerment and the other welfare measures undertaken by the National Democratic Alliance (NDA) government in the past five years.

Alleging that the Congress' manifesto does not refer to the poor and the middle class, Jaitley said the campaign materials will also highlight the BJP's commitment to these groups.

He said the BJP campaign would also dwell on the need for a decisive government with full majority.

"The country wants a strong leader. We want a government with one captain and not a team of 11 members with 40 captains," Jaitley said, taking an apparent dig at the opposition alliance in many states, including Uttar Pradesh, Bihar and Tamil Nadu.

The party also launched its campaign song -- "Chalo Ek Baar Phir Ham Modi Sarkar Banate Hai/Garv Ke Sath Desh Ko Age Badhate Hain/Phir Se Kamal Khilate Hai" (lets elect Modi government once again, lets take the country forward with pride, let's help the lotus bloom again).

The BJP also released a few videos focusing on the government's pro-poor schemes and some of its tough decisions, including those against terror.

In the 2014 Lok Sabha elections, the BJP had achieved considerable success with slogans such as "Ab Ki Baar Modi Sarkar" and "Acche Din Aane Waale Hain."

Ninety-one parliamentary constituencies spread over 20 states and Union Territories will go to the polls in the first phase on April 11.

The seven-phase Lok Sabha elections would end on May 19. Counting of votes will take place on May 23.