Jessica Simpson marked her 40th birthday by posing in a 14-year-old pair of jeans.

The 'I Wanna Love You Forever' hitmaker posted a snap on Instagram in the True Religion denim which has been in her wardrobe for the past 14 years.

Jessica wrote in the caption: ''I have kept these throwback True Religion jeans in my closet for 14 yrs (I'm not exaggerating!).

''I figured that since I'm in the final hours of my 30's I'd give them another try, and hello 40, so nice to meet you.''

It is the latest snap taken by Jessica, as last month, she posed on a beach in a bikini and hat as she prepared to say farewell to her 30s.

She accompanied the image with: ''YEE-HAW to my final days in my 30's. (sic)''

Jessica recently hailed husband Eric Johnson as her ''perfect soulmate'' as the couple celebrated their sixth wedding anniversary.

The star took to Instagram to give a behind-the-scenes insight into her and Eric's celebrations, holding up a giant, purple crystal butterfly that Eric had given her.

She wrote: ''Eric Johnson, my Husband, I love you. 6yrs ago today I married my perfect soulmate. Our unity was written in God's sky of colliding stars.

''Together we manifest dreams, nurture desire, and hold space. Destined, it always has been and always will be, forevermore. Also, anyone who knows me at all knows that this crystal butterfly is my dream gift [butterfly emoji] ... Whatever our souls are made of, his and mine are the same. (sic)''