It also claimed that many BJP leaders were afraid of speaking against the dispensation, fearing that they would have to face "unknown dangers" if they did.
The attack by Mr Sinha, who was the finance minister under the Atal Bihari Vajpayee-led NDA government, in a newspaper article has set off a political storm even as two top Union ministers asserted that the Indian economy was the fastest growing in the world.
"Some people assume development will take place by winning elections and by tampering the EVM machines or by using money power. But, the state of the economy is very critical now," the Sena claimed in an editorial in party mouthpiece 'Saamana'.
"When experts like Manmohan Singh and P Chidambaram tried to reveal the condition of the economy, they were written off.
Now, senior BJP leader Yashwant Sinha, who for a long time held the finance portfolio, has made some revelations. He may be termed dishonest or anti-national now," it claimed.
"If Yashwant Sinha is wrong, prove that the allegations levelled by him are false. Many other senior BJP leaders have strong resentment towards the failing state of the economy but cannot say anything due to the fear of unknown dangers," it claimed.
The BJP's paid social media 'pracharaks' will not be able to prove Mr Sinha wrong as he is a senior leader, the Sena said. While several schemes are being criticised for failing to meet the objectives, the government is spending crores of rupees to make them seem as successful, it alleged.
In the article headlined "I need to speak up now", Yashwant Sinha, 84, had criticised Finance Minister Arun Jaitley over the "mess in the economy" and said he would be failing in his national duty if he did not speak up.
Mr Sinha, a member of the BJP's 'margdarshak mandal' that was set up in 2014 to guide the party, also said a revival by the time of the next Lok Sabha elections due in 2019 was "highly unlikely" and a "hard landing" appeared inevitable.