Ashlee Simpson has hit back at recent stories surrounding her sister Jessica's substantial weight gain.

The younger Simpson - who gave birth to baby Bronx-Mowgli in late November - is jumping to the defence of her elder sister, who in recent weeks has been looking curvier than usual.

Jessica stepped on stage at a country music concert in Pembroke Pines, Florida, this weekend wearing tight unflattering jeans and a thick belt.

New mum Ashlee leapt to Jessica's defence on her blog, saying:

I am completely disgusted by the headlines concerning my sister's weight.  A week after the inauguration and with such a feeling of hope in the air for our country, I find it completely embarrassing and belittling to all women to read about a woman's weight or figure as a headline on Fox News.

All women come in different shapes, sizes, and forms and just because you're a celebrity, there shouldn't be a different standard.

Is this something you would say to your wife, daughter, mother, grandmother, or even a friend?

I seriously doubt it.

How can we expect teenage girls to love and respect themselves in an environment where we criticize a size 2 figure?

See Jessica's changeing weight below